I don't understand these Markings on the S/42 G

[Britton]

The Serial number is 64 and it is all matching except for the magazine, there is some kind of letter under the serial number in front of the frame, but I can't tell what it is, maybe a "b". I am trying to figure out the marks on the right side of the frame just above of the trigger, they look to be proof marks and a serial number"2222". I can't find any import markings anywhere. Any info would be appreciated. Yes, I shot it and I like it!