The Dodge-book written by Emile Becker and Guy Dentzer says that there
were 2 kinds of mounts used.
The M24 or M24-A1 is a postmount (I have one on my WC-51), and the
M50, which is a ringmount and was used on the WC-62/63 (very rare,
Gerrit Hemelman the Keep-Them-Rolling-Boss has one).
So there is only one mount that you can put on a WC-51.
regards
Auke Dijkstra