N#130757 Coin Diameter Range

Hello, I recently acquired an 1871 (Year 4) Japan 50 Sen (large type) coin.  I measured the diameter with a caliper and realized that my measurement was .63 mm more than the measurement of 31.51 mm, which is provided in the Numista listing (N#130757).  The weight of my coin is 12.45 grams, which is very close to the Numista-provided data of 12.5 grams.  Since it is a milled coin, is it normal for the diameter to vary so much?  Thanks.

The 31.51 mm value comes from the Japanese JNDA catalog and is most likely the official standard that was set for them (in THIS News Paper 1.25 inches/31.75mm diameter is stated, and an allowed deviation of 4.25g per 1000 coins).

The first type issues are not the most consistent in their production (things were still dialled in and people were learning) but these coins are also prolifically forged so you have to be vigilant and test more then just weight and diameter.
 

I have a M3 specimen with a diameter of 32.3mm and a very slight overweight, the M4 couldn't find any measures but I'll have a look tomorrow. Both are straight edge coins ]. 

Edit: My M4 specimen is 32.20 mm in diameter.

My M4 50sen is 32.25mm diameter and the weight a little lower at 12.338g. 

I probably will change the diameter at least to the size mentioned in the newspaper (really nice how detailed the information from national mints were at that time when money was still worth something 😅) and add a comment about the possible deviations. With the +/- 0.5 mm search tolerance these sizes should at least hit the coin page. 

Thank you! I appreciate the information.  I look forward to contributing as I learn more.