How do you tell a bronzed proof and a copper proof apart.......

[1949threepence]

..........in the absence of a reliable description?

There obviously must be a way, but it's not at all obvious to me. Two pictures follow, the second one on a separate post because I can't get them small enough to get onto one post. 

One is a P1326 bronzed proof, and the other is a P1327 copper proof. Can anybody point to the difference?

Neither of the coins is mine.

 

 

[1949threepence]

[Nick]

If I had to guess, I'd say copper in first picture, bronzed in second.

[copper123]

Same here .

Love the bronzed proof

[1949threepence]

21 minutes ago, Nick said:

If I had to guess, I'd say copper in first picture, bronzed in second.

 

1 minute ago, copper123 said:

Same here .

Love the bronzed proof

Needless to say, you're both correct.

But it's your reasoning I'm interested in. What is the identifiable difference?

[Peckris 2]

36 minutes ago, 1949threepence said:

Needless to say, you're both correct.

But it's your reasoning I'm interested in. What is the identifiable difference?

That was my vote too. I'm guessing that a copper proof is lustred, whereas a 'bronzed' proof has the unlustred natural bronze finish. I'll just wait for @Rob to come along and give a different reason! In which case I'll go with his superior knowledge.

[Bronze & Copper Collector]

3 hours ago, Nick said:

If I had to guess, I'd say copper in first picture, bronzed in second.

Ditto...

Gut feeling based on very little experience.

I would suspect, however, that a coin that has been bronzed would NOT display any luster (lustre). I think it might also display a slightly different surface texture.  Whereas a coin as struck, would display some natural luster, at least until it disappears with handling or age.

[1949threepence]

8 hours ago, Bronze & Copper Collector said:

Ditto...

Gut feeling based on very little experience.

I would suspect, however, that a coin that has been bronzed would NOT display any luster (lustre). I think it might also display a slightly different surface texture.  Whereas a coin as struck, would display some natural luster, at least until it disappears with handling or age.

This one is described as a bronzed proof, yet seems to have lustre.

I suppose my underlying point here is whether it's worth buying another proof of the same date, on the basis that it's bronzed rather than copper? If it's a gilt proof, no problem as they are very obviously gilt. 

[Sword]

Is there a significant difference in price between the bronzed and copper? If not, then it might not be worth the expense to get both as they have similar desirability and look virtually identical. However, if you really like the coin, then the existence of two versions is a perfect excuse to get one more. 

[Peckris 2]

12 hours ago, 1949threepence said:

This one is described as a bronzed proof, yet seems to have lustre.

I suppose my underlying point here is whether it's worth buying another proof of the same date, on the basis that it's bronzed rather than copper? If it's a gilt proof, no problem as they are very obviously gilt. 

They seem to have hedged their bets, describing it as "bronzed copper". I'd guess even they aren’t sure.

[1949threepence]

45 minutes ago, Peckris 2 said:

They seem to have hedged their bets, describing it as "bronzed copper". I'd guess even they aren’t sure.

I think that's right.

I've spent much of today looking off and on at copper and bronzed proofs. The only truly consistent difference I can make out is that the bronzed proofs are slightly darker in finish. 

[Bronze & Copper Collector]

15 hours ago, 1949threepence said:

This one is described as a bronzed proof, yet seems to have lustre.

I suppose my underlying point here is whether it's worth buying another proof of the same date, on the basis that it's bronzed rather than copper? If it's a gilt proof, no problem as they are very obviously gilt. 

The assumption is that the cataloger got it correct. Granted that they have MUCH MORE experience than I have, and I am loathe to dispute their attribution, but we all know that mistakes occur.  Caveat emptor.

Edited September 24, 2021 by Bronze & Copper Collector

[Rob]

On the OP - copper first, bronzed second.

23 hours ago, 1949threepence said:

This one is described as a bronzed proof, yet seems to have lustre.

I suppose my underlying point here is whether it's worth buying another proof of the same date, on the basis that it's bronzed rather than copper? If it's a gilt proof, no problem as they are very obviously gilt. 

That's bronzed, but depending on the lighting angle as a result of the surface not being planar, it is possible to get considerable apparent variation in colour which is not always obvious in hand.

10 hours ago, Peckris 2 said:

They seem to have hedged their bets, describing it as "bronzed copper". I'd guess even they aren’t sure.

Bronzed copper is correct. The flan is copper with a chemically produced bronzed finish.

In hand it is usually fairly easy to say which is which, with the caveat that there will always be one of two which are a little ambiguous. The main thing is to ensure you are comparing apples with apples and not pears, because depending on the period in which a coin was struck, the bronzing can vary in colour. Toned copper examples however are reasonably consistently dark in colour with any multi-hued colours depending on the lighting angle. I've put a few things together to show some differences, but given there is variation even within a period, don't take these as definitive examples.

The main point is that bronzing is done to produce an even surface colour which doesn't exhibit the greater variation in toning seen with copper. Medals are frequently bronzed for this reason. Obviously, when you have full red surfaces, the coin is clearly copper and not open to question.

This will take a few posts, so bear with me. Sorry they are all unfashionable halfpennies and not pennies, but the same principles apply.

First up is an Early Soho bronzed (P935) left, compared with a Late Soho copper (P973) right. As you can see, the bronzed finish has an even colour across the surface.

[Rob]

Next is an Early Soho bronzed compared to a Late Soho bronzed. Late Soho are appreciably lighter in colour than Early Soho with most a little darker than the P1370 shown on the right, but all are not as dark as the Early pieces.

 

[Rob]

This is a comparison between Late Soho copper (P1367) and bronzed (P1370).

 

[Rob]

When you get to the Taylor restrikes, the difference between the two finishes is quite obvious, but his bronzing shows considerable variation in quality. This shows a bronzed (P1161) and a copper (P1169).

 

[Rob]

An example of the inconsistent toning is shown here with a P1161 showing blotchy bronzing (left), compared to the well executed P991 (right). 

[Rob]

You sometimes see a red residue resembling jeweller's rouge in the recesses as in the G, E and stops at the base. This is probably remains of the chemical used to produce the bronzed finish. As you can see, the bronzing on the R42 (P1053) is much lighter than the previous post. A comparison has been made with the same P991 obverse.

 

Edited September 24, 2021 by Rob

[Rob]

For completion's sake, a pair of RM products, the 1867 bronzed proof and the 1879 toned bronze proof clearly shows the uniformity achieved with bronzing compared to the toning variation seen on the second coin. As stated earlier, when there is full original lustre, the copper (or bronze) attribution is unambiguous, but the main thing to look for is the evenness of colour/toning. Copper can tone in a multitude of ways. Bronzing reduces its ability to do so. Hope this helps.

[Mr T]

34 minutes ago, Rob said:

Bronzed copper is correct. The flan is copper with a chemically produced bronzed finish.

What is the process for bronzing a copper coin?

[Rob]

34 minutes ago, Mr T said:

What is the process for bronzing a copper coin?

I don't know. I've looked but can't find anything written down. Logic says it has to be a fluid to ensure even coverage because anything else would give inherently patchy results, but whether that is a chemical solution or reactive atmosphere, I'm unsure. The Taylor restrikes sometimes have what appears to be powder residue in the recesses, which I think may be dried out bronzing agent due to insufficient washing after application.

[oldcopper]

42 minutes ago, Mr T said:

What is the process for bronzing a copper coin?

I think the secret died in the 19th century, and no official bronzed proofs have been made after 1867 (though some say some 1877 farthings are bronzed - that would need to be seen in the flesh.

[Rob]

5 minutes ago, oldcopper said:

I think the secret died in the 19th century, and no official bronzed proofs have been made after 1867 (though some say some 1877 farthings are bronzed - that would need to be seen in the flesh.

Both Taylor and Moore were producing bronzed pieces up to the mid-1880s. The process has to be the same as for medals, or for that matter, mint toned farthings and pennies. The colour differences will probably be down to the list of solution ingredients.

Edited September 24, 2021 by Rob

[1949threepence]

1 hour ago, Rob said:

On the OP - copper first, bronzed second.

That's bronzed, but depending on the lighting angle as a result of the surface not being planar, it is possible to get considerable apparent variation in colour which is not always obvious in hand.

Bronzed copper is correct. The flan is copper with a chemically produced bronzed finish.

In hand it is usually fairly easy to say which is which, with the caveat that there will always be one of two which are a little ambiguous. The main thing is to ensure you are comparing apples with apples and not pears, because depending on the period in which a coin was struck, the bronzing can vary in colour. Toned copper examples however are reasonably consistently dark in colour with any multi-hued colours depending on the lighting angle. I've put a few things together to show some differences, but given there is variation even within a period, don't take these as definitive examples.

The main point is that bronzing is done to produce an even surface colour which doesn't exhibit the greater variation in toning seen with copper. Medals are frequently bronzed for this reason. Obviously, when you have full red surfaces, the coin is clearly copper and not open to question.

This will take a few posts, so bear with me. Sorry they are all unfashionable halfpennies and not pennies, but the same principles apply.

First up is an Early Soho bronzed (P935) left, compared with a Late Soho copper (P973) right. As you can see, the bronzed finish has an even colour across the surface.

 

Yes, that makes the comparison easier. Thanks.

[Bronze & Copper Collector]

A HUGE Thank You to Rob for that exceptional explanation (as always).

I'll toss in my nomination to have Rob elevated to Professor Emeritus, resident Guru, some such title to recognize his enormous contributions to our knowledge base.