Jump to content

Proper way to measure ancient coins?


CPK
 Share

Recommended Posts

Posted · Supporter

Just curious, since ancients often tend to come in irregular shapes, what is the "proper" way to measure the diameter? Longest, shortest, or just try to average?

Thanks!

  • Like 2
Link to comment
Share on other sites

  • Benefactor

If the shape is irregular enough that the differences matter, you'll sometimes see both given; i.e. 16mm x 10mm or the like. In less extreme cases, I tend to measure the longest dimension. I honestly don't know though if that's any kind of "norm" or simply personal preference.

  • Like 11
  • Yes 1
Link to comment
Share on other sites

 

I agree with Phil - I don't think there is a strong norm.  I recently bought a coin that said clearly "16mm (max)" - I like the clarity of this, but don't usually see it.  I have usually put both max and min (e.g. 32mmx39mm) when the coin is very oval.  Most coins I try to record the avg diameter.  Here's one where I felt I needed to share both dimensions.

upload_2022-3-27_7-47-24-png.1460487

Caria, Alabanda, Circa 169-161 BC, AR Tetradrachm (32-39mm, 16.2g, 12h), in the name and types of Alexander III of Macedon, Dated CY 1 (168/167 BC)
Obv: Head of Herakles right, wearing lion skin
Rev: Zeus Aëtophoros seated left; in left field, Pegasos springing left; A (date) below throne.
Ref: Price 2460

  • Like 10
Link to comment
Share on other sites

Posted · Supporter

Thanks for the replies!

I've been kind of averaging the measurements, but I like the idea of just measuring the maximum and labelling it as such.

 

  • Like 3
Link to comment
Share on other sites

43 minutes ago, Phil Davis said:

If the shape is irregular enough that the differences matter, you'll sometimes see both given; i.e. 16mm x 10mm or the like. In less extreme cases, I tend to measure the longest dimension. I honestly don't know though if that's any kind of "norm" or simply personal preference.

FWIW this is exactly what I do too.

  • Like 3
Link to comment
Share on other sites

I always thought the convention is to measure width at widest point, as well as at narrowest point if coin is too far off round.

However, for late roman bronze at least, the only useful measurement is the diameter (from center to center) of the beaded/pearl border, sometimes called PRD (Pearl Ring Diameter).

The reason the PRD is useful is because this was controlled on the die and reflects the targetted coin size for that issue. It's quite common for two bronze issues to vary only in PRD (maybe only by 1mm) and average weight (# coins per pound weight), and given the large variabiity of individual coin sizes and weights, the PRD, being the only controlled parameter, is the only reliable way to tell such issues apart.

 

Edited by Heliodromus
  • Like 9
  • Yes 1
Link to comment
Share on other sites

I usually just go with the widest too, but as some have pointed out above, for some coins it's better to go with two measurements...

 

1518204718_PhoeniciaArados-ARShekelGalley2250.jpg.c749cd0f4b1b50443903988b8abbe014.jpg

PHOENICIA, Arados
AR Shekel. 10.48g, 23.8mm x 15.4mm min.
Circa 420-400 BC. E&E-A Group III.1.1, C13; HGC 10, 29.
O: Laureate head of Ba’al-Arwad right.
R: Galley right, Pataikos on prow, above waves; M A (in Aramaic) above.

  • Like 8
Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

 Share

×
×
  • Create New...