In 1932 the German Army did not have the K98A in service anymore.
You should have a close look for an additional stamp on your sling. Most likely made for Police, Bahnschutz or similar organization.
The keeper is marked OK1851, Otto Koberstein since 1851. That's a marking that's was in use later in time, possibly during WWII. It probably had originally a keeper with brass stud.
I might sold some of these keepers to my friend Waffenmeisters (he has a website).