Απόσπασμα: "ZacUK" My guess is the number of lines.
So if the edge reeding is thick then there would be less lines per centimetre -
or if it was thinner then there would be more - so 21 or 26 per cm - maybe?
Yes, that's exactly what it is, the amount of reeds on the edge per cm:
But luckily, you don't have to count them if you have both varieties . Just take them together and turn the coins till 1 reed is at the same place for both coins. Then compare them. There are only 2 different, 21 reeds per cm and 26 reeds per cm, so if the reeds are further from each other it's the 21e/cm, if they less far from each other it's the 26 e/cm. If you only have one coin you really need to count.