ozjohn

I suspect the RM is competent to make sure their silver alloys are correctly prepared for coin making. They have been doing it for a long time.

A couple of typos: Should read: Any BLACK deposits on sterling silver coins even if they were Cu based ……………….. I also contacted Sterling and Currency …………. No a Sorry if there is any confusion caused.

Mostly Cu. However to separate the Cu from the Ag you would need something to break the bonding of the component elements that are sharing their valency electrons. For example oxygen blown thru the molten alloy that would turn the component metals into their oxides which could then be separated. The original assertion was that a coin with some black marks on it was affected by verdigris. The first thing is verdigris is green not black. Green Cu compounds indicate that they are cuprous (valency 2) not Cupric (valency 3) which are black. Verdigris is associated with cuprous Cu compounds as it is green. Any deposits on sterling silver coins evenif they were Cu based would not be verdigris Ag oxides and sulfides are black and these are what you normally find on tarnished (toned) silver coins. I think my chemistry is ok but it has been a long time since I have had anything to do with it. I also contacted a Sterling and Currency in Fremantle a coin dealer who has been in the business for several years on this question for a practical opinion. In their opinion they had never seen verdigris on sterling silver coins. I also found a reference that Cu could leach from very old silver coins but here they were talking about coins several hundreds of years old and I do not think 1917 qualifies for that age.

I hear what you say but what you observe does not mean the Cu is leaching from the silver coin. It is most probably from external contamination. Alloys of metal form electron bonds between the component metals that introduces chemical stability to the alloy This is what makes the leaching of the component metals unlikely. I suspect this is true for even 50% silver alloys used after 1920. For example dental amalgam which is basically an alloy of silver, mercury & copper (50% Hg, 30% Ag, 14% Cu plus a little Sn thrown in).. If this alloy leached mercury in any appreciable amount we would all be mad or dead.

Just a thought. Perhaps a little off subject it would be nice if the Royal Mint produced a frosted proof 1970 last of LSD struck in silver so we could see how those horrible Cu Ni. coins would have looked like if they were struck in a decent material as the Royal Australian Mint does with its masterpieces in silver offerings.

Looks like it has been struck over the flaw. Of course it is hard to be 100%.

Looks like this coin from NZ of which I have been tempted with but resisted with difficulty .https://www.colonialcollectables.com/uk-coins/607-1921-penny-unc-outstanding-coin.html Nice buy.

I have conducted some research regarding the possibility of verdigris effecting modern sterling silver coins. I contacted a well respected Australia dealer in British and Australian coins who has been trading for several years and has never encountered this issue. A paper which suggested that leaching of Cu from coins could take place over several hundred years. but not with modern coins and in addition no evidence has been presented by youliveyoulean to support his assertion. The only conclusion I can arrive at is this is b@@ @@@@t and should be ignored.. I rest my case.

Verdigris? It's lurking everywhere so I have been told.

I had a good look at the coin in question especially the black around some of the lettering. The black indicates to me that it is silver sulfide ie normal tarnish with a bit of dirt thrown in as verdigris would be green as it is copper based. It seems that the jury is out on verdigris on .925 silver coins. If you have any examples of copper based verdigris on sterling silver coins perhaps you would like to post some pictures illustrating this. I hear what you are saying but yet to be convinced.

No need to be sorry. A discussion on the possibility of verdigris affecting silver coins is a perfectly valid discussion. All I can add is in my experiance I have never seen it.

As I say in my experiance I have never seen it on any coins I have. In any case the original charge was veridigris on the coins in question in this thread. IMO verdigris is completely absent from all the coins discussed in this thread and is NOT an issue to the discussion.

What is being stored correctly? If you mean being left in a bag for 20 years and then seeing the light of day without any verdigris forming on both 0.925 and .500 silver coins ? Like I say I find your argument in convincing.

Unlikely on sterling silver 0.925 pure of which of which coin in question is made from. As an aside I have never seen verdigris present on . 500 fine debased British silver either.

Verdigris? I think need to study your chemistry my friend. Verdigris sffects Cu not Ag!

A PCGS MS 64 1917 halfcrown listed on Ebay for comparison. https://www.ebay.com/itm/GR-BRITAIN-George-V-1917-AR-Halfcrown-PCGS-MS64-SCBC-4011-ESC-758/173275070299?hash=item2857ffbf5b:g:vHgAAOSwqMRa1gVK Sword IMO I think your example is much better than the PCGS example listed on Ebay and I would be very happy to own a coin like the one you have .The PCGS TPG has put the "wear" on the ear, side of head and top of shield in the Ebay listing down to a weak strike.

This looks like a replica being passed as genuine. Any ideas? A fraudulent listing ? https://www.ebay.co.uk/itm/Queen-Victoria-Half-Crown-1-2-1900-Good-Condition/362302356594?hash=item545ae73c72:g:-vkAAOSwLLZa31sV

Very nice coin Sword and interesting comments regarding strike quality of coins. I examined the NGC MS 62 coin again with a eye glass and it appears the obverse area on the side of the King's head above the beard is weakly struck as is the corresponding area on the reverse where the top RHS of the shield is located. It is obvious that minting issues are not initially considered by NGC during their grading of process although it probably effects their final assessment of awarding MS 61 etc. as I think they grade first the rough grade F,VF,XF or MS ie Fine 25% of design remaining, Very Fine 50% etc. to Mint State 100% of the design present then they micro grade based on strike quality, lustfre etc. What a difficult series to grade as wear and strike quality are very difficult to tell apart. One criteria that I use is to examine the milling for wear as that for the most part is unaffected by the minting also many George V coins seem to have a thin ridge around the edge of the milling which is the highest point of the coin and will wear first. Coins that have the milling and the ridge I describe intact but seem to be worn are probably weakly struck and not worn. On the coin of concern the milling is hidden by the slab.

Two 1917 halfcrowns I have. The top one is a NGC MS 62 while the other is an ungraded coin I brought from Michael Coins before it closed when I was in London a few years ago. I think the ungraded example is a better coin than the NGC graded one and welcome any comments as I am trying to improve my grading skills. The top coin is the NGC MS 62 graded coin while the bottom coin is the ungraded coin brought from Michael Coins. Thanking you in advance for any replies

Thanks VickySilver. I noticed an error in my post. It should read MS 62 not MS 52.

I also had the same issue with a NGC slabbed 1922 MS 52 halfcrown.. I removed it from the slab and cleaned it with the Al. foil bicarb. of soda method and the results presented below. I know silver dip has been recommended but I think the foil method may be less destructive to the coin as it converts the silver sulfide directly back to metallic silver while emitting sulfurated hydrogen gas while silver dip is an acid that will etch the coin to remove the tarnish including some of the surface of the coin.I have previously posted these pictures but they seemed to relate to this discussion.

To clean or not to clean. That is the question? All I can say is any piece of silver left to its own devices for over a hundred years will tarnish. Put another way any silver coin with some age on it that is bright has probably been cleaned. You can try a silver dip or bi carb of soda and Al foil with hot water but I fear the spots my take longer to remove and in doing so may remove the tone you wish to keep.

Perhaps the UK and Australia should abandon the UNC, EF etc. and it's attendant undefined micro grades abt. near and adopt the Shelden scale which offers a far more systematic method of grading coins. 0 - 100 scale adopted by CGS offers a similar advantage however given that the Shelden scale has been in place for a long time it should be adopted in favor.

Not sure how this extra post occurred. Probably better if this one was removed. OZJOHN

Nice coin Paulus. I haven't noticed the thicker rim you mention although I have both varieties of this coin. It was the matte finish of the obverse that caught my attention. May still be a good buy for someone looking for an upgrade.