cobra, thanks for adding the coins
Citation: Makake77"Knob on the 2" means something like a serifed, stylized letter "2". it has a point/knoblike
feature on the lower right base of the digit.
The plain one just has a straight base without any design feature
hmm, not quite. On cobra's site, the serif on the lower right of the 2 appears on both versions. The difference is the "knob" or "drop" on the top left of the 2
https://en.numista.com/catalogue/pieces6557.html
it says 1957 has "6.5 mm 10" and from 1958 "7.0 mm 10"
I don't know where to measure this. I have coins from 57, 58 and 63
the height of the 0 is 7 mm for the 57 and 58 coins and 7.5 mm for the 63 coin
the horizontal size of the 10 is 9.0 mm (57/58) and 9.5 mm (1963)
the 1957 and 1958 coins are the same, but the 1963 coin has a larger 10
the 1963 coin has also a bigger overall size, the diameter is 23.5 mm compared to 23.0 mm for the other ones