When you see a receiver proud of the frame in front it's often evidence that the frame's serial number has been removed and changed.
In the USA, that act is frowned upon by the ATF.
Besides, the concept of a "Swiss Navy" is a little like adding Nebraska to a SCUBA diver's bucket list... Of course, I'm sure Lake Lucerne has a packet mail steamer...
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Igitur si vis pacem, para bellum -
- Therefore if you want peace, prepare for war.