I was wondering about that too so I did a quick search and this is what I found: "The Model 33/40 is the German version of the Czech Model 33 Carbine and was manufactured at Brno in occupied Czechoslovakia. Used by German mountain and paratroop divisions, some have a metal attachment on the left side to assist mountain and ski troops." http://www.rememuseum.org.uk/arms/rifles/armmoc.htm