Nice looking machine. It looks like you may be using 3-in-1 oil. Most will tell you to keep it away from sewing machines. You need regular sewing machine oil or Tri-Flo oil.
I'd say it was a 66-4. It looks like there may be a few discrepancies between the two lists. Here is a page from the 1924 catalog for Singer sewing machines -
https://www.sil.si.edu/DigitalCollec...s/image209.htm
There are lots of sites and videos of how to install a treadle belt.
Actually, I lived in Holcomb so a little west of Garden City (5 miles) .
Janey - Neat people never make the exciting discoveries I do.
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