This one must be an "S and M" tractor, it brings joy and yet is painful to own also! Have to forgive me, not even knowing what the M models were??? I some cases you can make a Speedex into diff models by making a few changes is all. Like engines, hood tins, type of drive/trans, etc. I have what I thought was a 1630, but might be a LATE S24 with the barn hood according to an expert. Looks like same tractor as the 1630, with a 3spd trans and I think I'm gonna build it as one. Can't seem to find any stamping in frame like most are supposed to have. Heck, clean it up, make it work, Who Cares what actual model it is, long as it looks like a nice Speedex when done?