YOU PICK /U CHOOSE LOT, ANY VINTAGE SINGER SEWING MACHINE KEY, FEATHERWEIGHT
I AM NOT A LOCKSMITH NOR AN EXPERT ON WHICH KEYS FIT WHICH LOCKS SO YOU MUST BE THE DECIDER OF THAT CHOICE! #17,18,19,20 have SQUARE shaft heads. #1,2,3,4 fit most 1938-1948 model 221 & 222 black cases.