Look what I found at a thrift store for $25. It's not for me, it's for a friend who is wanting a hand crank sewing machine for her daughter. It is an old treadle head that needs to be converted. It is a Singer, Serial number EM285899 and model number 15K80. If you know what it is called will you please let me know?
Update: Captain Dick of treadleon.net says that it is a "That is a Model 15 of older vintage. This one is sometimes called the RAF model. It came along when other 15's were getting reverse, but it didn't win the lottery, so it has stitch length but no reverse, like the 15-30's."
Thank you Captain Dick!