Pepe,
Thanks for the new pictures.
Are we to understand that you are in Portugal?
Portuguese Navy Lugers are 9mm. From the barrel, this gun is in cal. 7.65 Parabellum. If it is a Portuguese model, that would make it a Portuguese Army Manuel the Second (M2) Luger. With the toggle open pull up on the front of the extractor, is CARREGADA stamped on the left side?
The front angle of the gun shows clearly that the front of the frame has been ground back, leaving the receiver to extend foreward of it a bit.
It is hard to tell from the photos, does it look like a proof mark has been ground from the left receiver? Is there grinding at the back of the frame above the lanyard loop?
Could you please show us some more pictures? A closeup picture of the bottom edges of the takedown lever and trigger plate...a closeup picture of the bottom of the receiver (dismounted from the frame) including the barrel near the receiver...a closeup picture of the thumb safety with the lever in the "up" position. Thanks very much for taking the time and effort to show us so much about this gun.
The absence of markings such as the one removed from the top of the receiver means that the particular collector variation cannot be identified. As you suggest, this depreciates the value to a collector quite a bit. In the US this Luger would only be useful as a Luger to shoot.
The absence of the serial number, particuarly on the front of the frame, means that the gun would be difficult or impossible to transfer or own. In the US there are national gun laws, and also gun laws in each state. In order to own a gun whose serial number has been removed it is necessary to follow some specific complicated national regulations, and it may still not be possible to register such a gun in some states. It would be difficult if not impossible to import such a gun into the US from another country.
--Dwight