I've got a dremel cutting wheel and a file that is about the same width as that bandspring. It wouldn't take me long to notch a K98k band to fit. Is that band numbered to the rifle? Also, I do believe that the postwar Yugo Mausers are all cut for a side sling arrangement and utilized K98k bands. It seems to me more logical that the alteration was done postwar to a prewar yugo M.24. Look:
http://oldrifles.com/yugoslavian.htm
So, we know this is a German mod as opposed to a postwar Yugo mod, consistent with Yugo M.48s, etc., how?