The base of the cup is marked GGrGer, with the manufacturing code dwc and waffenampt WaA135 underneath the code. The schiessbecher does not have grooves, and can be disassembled into two pieces.
The schiessbecher will fit on a K98, and on a replica STG-44 with the muzzle nut removed. You may have to remove the sight hoods, though. The item "Reproduction WWII German schiessbecher and wrench for the K98" is in sale since Saturday, January 09, 2016. This item is in the category "Collectibles\Militaria\WW II (1939-45)\Reproductions\Germany". The seller is "cliffordtoadjumper82" and is located in Fayetteville, North Carolina. This item can be shipped to United States.