that is the FW plate - and yes, it will fit just about anything else too. By itself, it often sells for over $30 (darn FW people overpay for stuff all the time!)
When I FMQ with the 15, I drop the feed dogs and it works just fine. I use the hopping foot from Sew Classic too.
And yes, the 201 drops the feed dogs too.
That is why you don't find feed dog cover plates for the 15 and 201, but you do find them for the FW, 66 and 99.
It's kind of a pain to drop the feed dogs as you have to tip the machine to get at the screw on the underside.