Thank you all for the interest albeit lack of an answer. After a lot of hit and miss research the owner of the shotgun may have solved the riddle himself. The medallion was somewhat worn so the "snake" terminology may have misled our search.
We believe it is in fact the logo of Deutch Werke, so now the question is did DW produce any "Geha" style 98 Mauser shotguns? If DW did this I personally have never observed another but a logo switch would be easy.
Now with this new info. perhaps someone can add more. --- John
