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So there is no serial number on the actual steel bits, the action or "insides" , for want of a different term.


So in theory I could have a 9mm and a 357 SIG on the same loence?

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YES..the only serialized portion is the trigger assembly..

the video below should show a more clear idea of what I describe as it seems you and I have a bit of a language barrier..
https://www.youtube.com/watch?v=U2Q6q6HsNKE

The metal portion with the trigger is the only part with a serial number on it