Another check you can make to determine which model you have is to
check the model number of the motor (see the plate mounted on the motor).
Each of the four models of the featherweights were originally furnished with
a different motor.

Model 221-1 Model Series 3 Motor
Model 221K4 Model CAK7 Motor
Model 221K5 Model CAJ6-8 Motor
Model 221K7 Model CAK8-8 Motor

Another distinguishing feature of the 221K4 is it is the only
featherwieght model that has R.F. suppression with grounded wiring. All
that means is that it shouldn't interfere with radio or T.V. signals and
there should be a three prong plug to insert into the wall outlet.