WAG...here on my part...but is that a Simpson E/6 proof on the top side of the barrel. Thus a Weimar rework of an Imperial DWM luger ?
Looks like the proof stamp strike was not even, as the bird's head does not appear to show well...
Regards,
Pete... <img border="0" alt="[typing]" title="" src="graemlins/yltype.gif" />