Mauser was once officially called 'Waffenfabrik Mauser' (WM). In the 1920s it changed to 'Mauser-Werke A.G.' (MW). So a W and an M in the logo are to be expected.
The WR / RW logo is often seen in areas that had been inspected for hardness. A popular explanation for the logo is 'Werksrivision', but it is also tempting that it refers to the Rockwell hardness test
