I have a belt driven 201K, I can't say it stands behind either a 66 or 15 when it comes to capability. It's a bit easier to adjust tension on the CB bobbin case. For some odd reason, my 66 and 99 runs lighter and a bit faster. If it's with out feed dog drop on the bed is't a very early one, if it has a turn knob it is probably at least early to mid 1950s. The three push botton versions are a bit later. It's a bit tricky to date these, you can find pale blue versions with origial receipt as late as the 1960s, even 1970s. The later ones can still have the typical Singer 15 stitch length lever and chromed plastic turn knob for the feed drop; they can be white, cream, pink, pale blue, pale green,... The back version was common around 1950, and a bit into the 50 colors seem to have become more popular.