Suzelle, et al. I just became to owner of a Pfaff 138-6/21-BS. I purchased this machine and a Singer 600W1 complete with tables, motors and some bobbins. The Singer has a knee lift but the Pfaff doesn't. the total price for both of them was $150 so,even though I only wanted the Pfaff I figured I would also get the Singer and maybe sell it. I have been looking for a walking foot machine but this might do for now. I rewired the Pfaff with proper wiring and added a light as well. In researching this machine for whatever information I could get (I'm a researcher at heart) I came across a lot of good information but one site (blog) had some information about adding a foot operated reverse pedal. The Pfaff 138 has a feature that allows this. Here is a link to the thread that explains it. Hope it helps someone.
http://www.ashleyandthenoisemakers.com/blog/2015/3/7/pfaff-138-review-1
I plan to add it when I get to sewing on my 138.
Clem