There were hundreds of leather companies in Germany 1898-1945, often working in cooperatives, to identify the maker one would need a firm place to start, like the city. This looks like it might be Berlin, a rather large (huge) city with many firms engaged in leather products. Second we would need at least a partial name, - many wartime slings (from WWI) have depot markings rather than maker marks, yours is commercial and theoretically would be easier to determine if you could give better pictures (clear with distinct letters showing). I have not recorded many Berlin marked slings, but have recorded several Berlin firms engaged in other leather products, many of which probably made such a simple thing as slings. Unfortunately really nice original Imperial slings are elusive, their age and use/abuse, poor preservation methods have made them hard to find and therefore few to document.
Most of what we know about leathers makers (slings, pouches, saddles, cases, holsters etc..) are from WWII where surviving examples are many times more common. Naturally many firms disappeared in the interwar period, the vindictive treaties caused serious economic problems for Germany and the chaos that followed caused many business failures. (Generally, then as now, the government buy-bail outs, which were common in Germany 1919-1933, were for large firms, especially firms with large payrolls or export footprint, many of these small leather makers probably can't be traced by the larger WWII databases.)
