How would a person know they have a 201? It looks similar to 66 and 15-91 to me.

66 - Horizontal Class 66 Bobbin Left Side - Tension on the front
15 (90 or 91) - Vertical Class 15 bobbin - left side - Tension on the Left
201 - Horizontal Class 66 Bobbin Left Side - Tension on the front - Oval spool pin plate on the top - 201-2 is the easiest to pick out, it will be the only front mount tensioner machine to have a potted motor. To me, the pillar looks a little straighter than a 66 too. vssmb.blogspot.com has info on identifying them too, as does Sandman-collectibles.com.

The 101 also has front mount tension and a potted motor, though they are not very common.

You're right. I don't usually think of the 101, because I've never seen one in real life.

I have a1936 Singer 201k-4, original hand crank. I treadle it. My machine is almost silent and is a lovely machine. Here's a picture:

That stitch length adjuster is common to every 201 I've ever seen, and looks nothing like any of the other models.

What is it that's different Mike? It looks like the one on my old 15-91 and my current 15-90 to me. Perhaps I've been looking at it as the same but it's not?

[ATTACH=CONFIG]450395[/ATTACH]

here is Heathers 201-2
[ATTACH=CONFIG]450405[/ATTACH]

Thanks Tammi. Seems your later model 15s had the same stitch length adjuster as the 201. I only have one model 15 and it's quite early.
201s I've found easy to recognise, but for certainty nothing beats looking up the serial number ;)

Don't think we ever had the 201-2 in Australia. I've never seen one anyway. Guess it's distinguished by the light at the front?