May be a Singer 201. My daughter just purchased one for $50 at an estate sale. Supposed to be as good as a 221 (typical Featherweight). Certainly light enough.
I believe the machine, built at the same time as the traditional Featherweight (judging from the serial number on my daughter's machine) was designed to go in a cabinet, but has the bentwood case in order to make it portable.
Congrats on a good find!