This Caille Model 30 also was a badge motor made for Sears and Roebuck and sold by them as a Motorgo. The only difference between the Caille  and Motorgo versions were decals.

The serial number, which is stamped on the cap on the flywheel begins with SR and this is the "tell" for Motorgo.  Caille used the letter "M" as a prefix at times with the same meaning. 

The Model 30 is one of the  easiest Cailles to identify because of the auxillary air intakes on the front of the motor on either side of the carb. They were used for increased speed.

Model 30s were shipped with a tractor prop, as well as the usual 3 bladed prop, which turned a fishing motor into a racer of sorts.

This particular example is in very nice original condition with the exception of the carb choke lever which is brass here.  It should be the same metal as the rest of the carb.  This motor also has the original tiller with the grip which is very unusual.  The air horn is also usually missing.