blued wood base mag ?

[pisto]

Hello there, spoke a while ago about a mag makes me wondering.
The condition is original I would say! I can�´t see any tool markings coming from disassampling ore something.
The sping is correct strawed and the pin seems to be never removed.
Anyhow it is a blued type with a wood bottom.
Also the bottom is proof marked! (don�´t come out in the picture very good)
Does anybody have a explanation for that?

will try picture in the nest message!

Regards