Hi Greg!
The Singer 17-23 is an old industrial cylinder bed machine with drop feed across the arm. Feed dog at left of the needle and roller presser foot. The machine was made for shoe production and smaller leather works. Max tread size is 20 and stitch lengths about 4 to 5 mm, but You have to ask seller if it takes heavier tread. You can find information on these machines on Singerco.com. Look under industrial products, there you can download old manuals on pdf`s. You can also find info on this link: http://www.industrialsewmachine.com/webdoc1/used/used-singers/17.htm the Singer 17 was not made for heavy leather works, to sew belts you will need a heavier tread size 12, 10 or 8, and a longer stitch. The Machine won’t handle this. In my country (Norway), you can find the singer 17 very cheap. You got to move up in class. Look at these classifications: http://www.ferdco.com/1/3.php. Depending on where you lives, but I recommends German Durkop Adler or Juki from Japan. Singer has the patents but not the quality. I have 3 singer machines my self. The biggest of them a Singer 144w 305 is made in USA has ok quality, the other 2 is made in Scotland are crap. I hope this was at some help!
Reg. Trox