Some GE history...
I took a closer look at the GE lineup and what I found was that the WA750 M (1955) and WA750 N (1956) were the TOL models and were the only ones with Filter-Flo. Your model--656--was one step down and featured the look the 750 without the FF. This was probably a special, or promotional model and was only offered in '56 N series line.
GE continued the 650 (dual knobs), 550 and 450's (single center knob) for '55 and '56 but bumped them down to the MOL and BOL models. These units remained relatively unchanged from the 1953 "K" and '54 "L" machines they descended from.
This is based on GE service literature. Someone with marketing lit. may have a different spin on this. If so, let us hear about it.