Gryphon,

You will find that Wannabebwana is correct and it is a bottle opener. You will notice that it is an old Mauser in the photograph which was made well before the invention of twist top bottles.

This also explains the reason you don't find these bottle openers manufactured into modern variants of the 98 Mauser (or any other modern rifle for that matter), as the old pop top bottle is a thing of the past, twist top bottles are the way forward.

Another reason the bottle opener was removed from modern manufactured 98 Mausers, was that in some obscure circles it was deemed as potentially dangerous to be drinking whilst shooting. This trend of not drinking whilst shooting has not yet caught on, as you can see when viewing this thing called YouTube.

Also, Tom H nails it when he says they couldn't be charger ports as O3A3's and P17's don't have them.

I'm not sure how thin the air is up in Colorado, but for 3DogMike to suggest it is a charger slot is just a ploy to try to confuse the more intelligent members of the community.

So Gryphon, I hope this clears up you query. Sometimes things are not quite as they first appear.

Regards