And if you compare that "
just OK wood for the cabinet in 1951" to what is available today it will be the same comparison as you just made from the early 1900s to 1951.
I have a Singer 5 drawer treadle cabinet made with stamped metal legs rather than the cast iron. The wood is the same and it's very solid. The machine in it dates to 1919. I don't know if the cabinet is the same ages as the machine.
I'd love to see a pic of your 1951 treadle. It's only a year older than me
Joe