Chamberlin M Series
How many? Richard Chamberlin has given me two numbers on two separate occasions. 300 M1's and 100 M1's. Who else are we gonna ask? Serial #'s don't help because they don't appear to be sequential. I have personally seen maybe 20 M1's, 5 M1 remotes, 5 M2's, 4 M4's and 2 Model 800 Rivieras. Suffice it to say that they're very hard to find but well worth the effort.