ok Singer only made to my knowledge one short arm big bobbin machine The 29U171. It was the first singer shoepatcher made in Japan. The 29K171, 172, 173 were the last ones made at Kilbowie Scotland plant.
Next came the 29U171 in Japan. The the last ones made for Singer the 29U171A, 172A, 173A. Singer did make one high lift model-the 29K21. They also made a few long stitch versions-29K10, 11, 16, 22, 23, 52, 54.