Die matches?

[Gavin]

So I’ve seen various threads on die matches, such as the one here: http://www.forumancientcoins.com/board/index.php?topic=102196.msg668087;topicseen#msg668087

A basic question: how does one determine a die match? Is it simply an “eye test” in which two coins seem to have the same features in the same place? Given the inherent similarity in types, it would seem very difficult to tell the difference between two coins struck by the same die and, say, two coins with the same obverse or reverse type. Is there some secret or dispositive feature that “gives away” a die match?

[Victor]

There are a few posts on this forum about die matches, including this topic with four die matches for an unofficial VLPP --
http://www.lateromanbronzecoinforum.com/index.php/topic,818.msg2746.html#msg2746

VLPP's from Trier
http://www.lateromanbronzecoinforum.com/index.php/topic,642.msg1861.html#msg1861

some more VLPP's
http://www.constantinethegreatcoins.com/diematch/





some FEL TEMPS
http://www.lateromanbronzecoinforum.com/index.php/topic,522.msg1451.html#msg1451

Die matches are found by recognizing coins that were struck using the same die.

Here is a bit about die matches from my unofficial coins page

"Die matches are generally not very commonly found when looking at Roman Imperial coins, however for unofficial coinage they are much more frequently found by collectors. There are two reasons that they are more easily found-- first, specifically talking about VLPP’s, they are numerous and secondly, given their nature, the styles vary so greatly, that die matches tend to stick out. They are more apparent than official coinage matches, which most certainly could have as many die matches floating around, but since official coinage styles look so similar, matches are only found when careful attention is paid to the coins."

http://www.constantinethegreatcoins.com/barb2/


So, it's easier to find die matches when you are looking at barbs, as the styles are so different that they tend to stick out. This contrasts with official coinage, where even with different dies, the style might be very similar, so it gets harder to find die matches. For rare issues though, it is easier to find die matches, as there may only be a few known examples and it is quite easy to match them up.

[Gavin]

"by recognizing coins that were struck using the same die" So, again, is it just a naked eye test? I guess that's a stupid question. I'm not sure how else one can recognize a die match. But, for example, the animated image above that toggles between two VLPP barbs presumably shows a die match. But those coins don't look similar enough to me for me to say, "Yep, that's a die match." Maybe it's just a skill that just appears one day after you've looked at your 10,000th VLPP coin.

[Victor]

Yes, you have to just look at coins with your naked eye. I pick a few distinctive points to match up and then move onto other things like the inscription. For a Siscia VLPP, I first look at things like the shield decorations and helmet design, these are easy to spot if similar. With an editing program, you can also do picture overlays. My gif is hard to match up because it is animated and the orientation for the two coins is a little off and the lighting for the two coins is also different; you would have to look at the pictures of the coins to really compare.

[seuk]

A program like Photoshop is a great tool in order to compare dies - when I've found two coins which seems to be coming from the same die I do a picture overlay as mentioned by Victor. That is: moving a picture over another picture you want to compare with - then reducing the transparency to 'round 50% sometime less or more depending on the light/darkness of the individual coin. Further the picture can be rotated in order to compare details more precisely.

[Gavin]

Ah yes, I can see how that could really help "scientize" the eye test a good bit.