Side Plate Question

[steven c]

I had read somewhere in the past these were numbered on the inside as well with it being numbered one number higher than the outside. I've got a 1938 S/42 here, it's not stamped on the inside, all the numbers match including the mag but not the firing pin. Maybe some of you guys could give me some thoughts on it. These are very specialized type guns.

One other question, the grip plates aren't numbered. The left side has a letter "O" at the top and a "R" in the middle. The right grip is stamped with a "S". Would they still be right for the gun?

Regards and thanks in advance, Steve.