Sling/Stock ID Needed

My Grandfather recently handed down an S/42g Mauser 98K he picked up off a dead German 88 crew after a skirmish on November 19, 1944.

Wrapped up in a baggy next to the 98k was a leather sling/belt. I originally thought this was the sling for the gun. However, it does not have a removable "keeper" but instead has what looks like a buckle.

It is marked Kog/44 and has the Nazi bird with what looks like WB 1927 written in tine letters underneath.

Does anybody know what this thing is. I do not believe this is a sling for an SG42 of STG 44.

Maybe it is a sling/carrier for an ammo can?

Any suggests would help. I checked the Rifle Sling Web Page listed here, Rifle Sling Home Page, but saw nothing.

Pictures attached.