I suppose we say straight shank when the referance point is a 401 or something like that, but for Singer it's usually low shank, high shank and slant shank to differentiate. As long as my mind is on this subject there's: super high shank, back clamps, side clamps, various different fittings for the presser foot between brands. The first lant shank was the 301 introduced in 1951.
When I bought the buttonholer for my 201, the seller dated it to 1947. It's the standard black one with cams. At first I assumed it was a 1950s version of it; it came in the green plastic box. Later I have read this plastic box was intruduced before 1950, it might be. I bought it on ebay from the US. It reminds me, I have complete the cam sets for it.
I think Greist made the carboard box well into the 1950s; and it looks identical to my Singer version of it.