It's a late model 66, at some point it was given the stitch length lever with backtack in sted of a chromed knob (apparently by 1948 in the least
) This lever might make it look like a model 201, but the 201 has a true revers, with a round plate around the lever in sted of the more square on the 66. Yours look very nice, the dull or crinkle finish doesn't turn up that often around here.