ID'ing M56 size?

[FinMC]

Hi all,

I'd like to know what the size of my M56 is, it doesn't seem to have the "I, II, or III" marking that indicates the size above the month and year of manufacture (it's rather hard to see in the photos but it is "4 63"

There is also an ink marking on the other side of the helmet interior, does this mean anything?

Would appreciate help on this from someone better versed with the East than I am!

Cheers.

[Gunny Hartmann]

A lot of these lids never had the size stamped into the metal, that ink stamp denotes size 3.