Mumra Posted October 17, 2017 Posted October 17, 2017 (edited) Ok so yes I'm new to metal testing and coins but this coin has got me stumped and in pretty sure I'm doing things mostly correctly. So it's got a hole from being a piece of jewellery it weighs 1.6 grams on my .1 weighing machine so that looks good it is also 17mm so another tick the for a gold 5 Franc 1867 coin. But then I check the coins photos and none of them are white gold so I'm thinking a copy or a silver coated coin or something so I start testing... The tests say no silver no base metal not 9ct then it gets harder... The results point to 18 - 24ct?! But it's silver / white gold colour? Finally I left some testing acid too long trying to test the inside of the hole and unfortunately it was stained kind of pink ish which I rubbed with a silver (impregnated with chemical) cloth which I was told would clean it but I'm left with a gold / bright copper kind of colour... See photos. I don't have any more other metal testing liquids so not sure if there is any other ones involved. So 1. Can I clean it back to white gold colour? 2. What is it? Thanks! 3 photos one before silver cloth two after : (will add soon I'm having trouble posting images) ...Ok this is the best I can do: https://imgur.com/gallery/goATF Edited October 17, 2017 by Mumra Quote
Rob Posted October 17, 2017 Posted October 17, 2017 I'm going copy. It looks too new and a copy would likely be plated copper. I have no idea who would make them this side of Shanghai, but there will be somebody somewhere. Maybe France? Quote
Mumra Posted October 17, 2017 Author Posted October 17, 2017 I think it's been cleaned before I got it but I tried rubbing a side and it's testing the same wouldn't copper give other readings? And how can 18 + ct gold look so white thanks. Quote
Mumra Posted October 17, 2017 Author Posted October 17, 2017 I think it's been cleaned before I got it but I tried rubbing a side and it's testing the same wouldn't copper give other readings? And how can 18 + ct gold look so white thanks. Edit: I ment I rubbed some of the darker metal off the side from under and it says gold on the test... I'll do some more testing I guess... Quote
Flash Posted October 17, 2017 Posted October 17, 2017 Don't forget chemical/acid testing is no-where near a reliable system. Plating, previous harsh cleaning, contamination, measurements or even a few specks of crap will skew the results. 1 Quote
Rob Posted October 17, 2017 Posted October 17, 2017 (edited) Given you are rubbing bits off left right and centre, why not take it to a bullion dealer and cash it in? There won't be much left soon. You can always do a specific gravity check. Alternatively, 17mm diameter, density of gold is 19.32g/cm3, density of copper is 8.96g/cm3 assuming it isn't alloyed with silver in which case use 10.49g/cm3, weight 1.6129g for the complete thing without hole, reduce the weight by about 7% for the hole, purity if it was gold would be 0.9000, volume of a cylinder is 3.14 x 0.852 x height. You can therefore work out if it is gold just by establishing the thickness, give or take a bit seeing as it isn't a flat disc. 19th century gold coins were not made from white gold. This is something driven by modern fashion tastes. It would be bog standard gold alloyed with bog standard copper or bog standard silver on a 9:1 ratio. Edited October 17, 2017 by Rob Quote
Mumra Posted October 17, 2017 Author Posted October 17, 2017 1 hour ago, Flash said: Don't forget chemical/acid testing is no-where near a reliable system. Plating, previous harsh cleaning, contamination, measurements or even a few specks of crap will skew the results. Hmm but I mean I'm getting 0 on the copper scale not even tiny fleks see here: https://imgur.com/gallery/rntXr The copper coin violently reacts... instantly green... the mystery French coin stays totally clear on all parts no reaction to this or the silver solution only the stronger 14 - 24ct solution and it's slow so on the higher end... :S Quote
Mumra Posted October 17, 2017 Author Posted October 17, 2017 1 hour ago, Rob said: Given you are rubbing bits off left right and centre, why not take it to a bullion dealer and cash it in? There won't be much left soon. You can always do a specific gravity check. Alternatively, 17mm diameter, density of gold is 19.32g/cm3, density of copper is 8.96g/cm3 assuming it isn't alloyed with silver in which case use 10.49g/cm3, weight 1.6129g for the complete thing without hole, reduce the weight by about 7% for the hole, purity if it was gold would be 0.9000, volume of a cylinder is 3.14 x 0.852 x height. You can therefore work out if it is gold just by establishing the thickness, give or take a bit seeing as it isn't a flat disc. 19th century gold coins were not made from white gold. This is something driven by modern fashion tastes. It would be bog standard gold alloyed with bog standard copper or bog standard silver on a 9:1 ratio. Well I only rubbed the bit that was broken already... Yes well I'll get a more accurate weight tester anyway but it's very close already... Maybe some other metal tests... And still 0 silver in tests. Thickness is around 0.5 0.6 mm thicker at the hole. Thx 1 hour ago, Flash said: Don't forget chemical/acid testing is no-where near a reliable system. Plating, previous harsh cleaning, contamination, measurements or even a few specks of crap will skew the results. Hmm but I mean I'm getting 0 on the copper scale not even tiny fleks see here: https://imgur.com/gallery/rntXr The copper coin violently reacts... instantly green... the mystery French coin stays totally clear on all parts no reaction to this or the silver solution only the stronger 14 - 24ct solution and it's slow so on the higher end... :S Quote
Rob Posted October 17, 2017 Posted October 17, 2017 But how thick is it at the moment? The thickness will tell you instantly if the material is anything like as dense as gold. Quote
Mumra Posted October 17, 2017 Author Posted October 17, 2017 3 minutes ago, Rob said: But how thick is it at the moment? The thickness will tell you instantly if the material is anything like as dense as gold. Thickness is around 0.5 0.6 mm thicker at the hole... because of displaced metal. Quote
Rob Posted October 17, 2017 Posted October 17, 2017 0.5 - 0.6mm thicker than what number? Without a thickness for the flan, you can't work out the volume and by extension the density. If you can calculate the density it will be obvious whether it is gold or not. I personally wouldn't hold my breath. 1 Quote
Mumra Posted October 17, 2017 Author Posted October 17, 2017 (edited) 9 minutes ago, Rob said: 0.5 - 0.6mm thicker than what number? Without a thickness for the flan, you can't work out the volume and by extension the density. If you can calculate the density it will be obvious whether it is gold or not. I personally wouldn't hold my breath. Oh I ment it's 0.5 to 0.6 mm total thickness in different places ... Did a few measurements. And yes I'm just doing all this to learn I think I'll try this in the future : https://youtu.be/xYdSEAm-7uI thx. Edited October 17, 2017 by Mumra Quote
Mumra Posted October 17, 2017 Author Posted October 17, 2017 2 hours ago, Rob said: But how thick is it at the moment? The thickness will tell you instantly if the material is anything like as dense as gold. Thickness is around 0.5 0.6 mm thicker at the hole... because of displaced metal. edit: ok so thickness of 0.6mm means gold I guess ... Or a really accurate copy :s Quote
Mumra Posted October 17, 2017 Author Posted October 17, 2017 I guess I need more investigation... I'll post back when I have something...I did wonder if it was real then coated in white gold recently or something else making it silver coloured... Anyway thx... Quote
Mumra Posted October 18, 2017 Author Posted October 18, 2017 Also I must say I was having trouble with my phone earlier and got a bit distracted. I meant to say it's about 0.6 to 0.5mm thick in total. And slightly thicker at the hole due to displacement (maybe 0.7mm ish total thickness at the hole). So it's looking like the correct measurements for this coin. I have new testing equipment on the way which will give better information... Thanks. Quote
Leo Posted October 19, 2017 Posted October 19, 2017 With the measurements that you have provided, if it was gold it should weight about 2.7g... Quote
Mumra Posted October 19, 2017 Author Posted October 19, 2017 (edited) 17mm by 0.6mm seems to be the exact size of a genuine one though. I saw this too: This 5 Francs coin features a bust of Napoleon III in profile and contains .0467 oz of pure Gold. Not sure if that's relevant. anyway I'll try the dangle in water specific gravity hopefully tomorrow. . It's looking like 1.573g on my new weighing machine on a quick try. Thx Edited October 19, 2017 by Mumra Quote
Mumra Posted October 20, 2017 Author Posted October 20, 2017 On 17/10/2017 at 4:48 PM, Rob said: Given you are rubbing bits off left right and centre, why not take it to a bullion dealer and cash it in? There won't be much left soon. You can always do a specific gravity check. Alternatively, 17mm diameter, density of gold is 19.32g/cm3, density of copper is 8.96g/cm3 assuming it isn't alloyed with silver in which case use 10.49g/cm3, weight 1.6129g for the complete thing without hole, reduce the weight by about 7% for the hole, purity if it was gold would be 0.9000, volume of a cylinder is 3.14 x 0.852 x height. You can therefore work out if it is gold just by establishing the thickness, give or take a bit seeing as it isn't a flat disc. 19th century gold coins were not made from white gold. This is something driven by modern fashion tastes. It would be bog standard gold alloyed with bog standard copper or bog standard silver on a 9:1 ratio. Ok so slightly upgraded equipment and the dangle test : https://imgur.com/gallery/pQfjj 1.571g weight 0.080g in water weight = 19.6375 gold I guess? Thx Quote
Unwilling Numismatist Posted October 20, 2017 Posted October 20, 2017 It's still plated. And by that I mean not gold or precious. My money, all $1.92 of it would be on aliexpress.com or similar. Quote
Unwilling Numismatist Posted October 20, 2017 Posted October 20, 2017 https://www.aliexpress.com/wholesale?initiative_id=SB_20171020090558&site=glo&g=y&SearchText=napoleon+iii+5+franc&page=1 Gold would be gold all the way, no-one plates gold. Silver likewise would not be plated with a top-coat of non-precious metal. Platinum wouldn't be worth it for such a small coin, and white gold is a 20th century .. I want to say trend, but that doesn't seem like the right word. Quote
Rob Posted October 20, 2017 Posted October 20, 2017 What I don't understand is why you don't just take it to a bullion dealer and scrap it. The hole will make it only worth melt whatever the outcome, and they will be able to tell instantly in hand whether it is gold or not. If a modern thing and made of so-called white gold, then it will still be worth bullion because it isn't original. The original gold coins would be struck in conventionally coloured gold, and if it was struck in platinum (not impossible, but doesn't explain the copper colour), then it would still have bullion value. The biggest bonus would be that you could get an unambiguous decent piece without a hole from the proceeds of the sale as it is the sort of thing you should be able to pick up for around the melt price. I'm not sure where this thread is going. You say you have a gold piece. Others think it is plated something. This isn't going to be resolved by universal agreement. Quote
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