it's a 15-30, the 15-90 will have reverse - this one is the older model with forward only. And yes, it would have come as an electric model from Singer.
the RAF makes it worth a bit more than the more common decal pattern. I was very, very happy to pay $75 for one like that in a cabinet for my collection - however the seller had been trying to sell it at a yard sale and craigslist, and no one wanted to pay that price until I came along - and I smiled all the way home (about 500 miles).
DO NOT LET THAT ONE GET TOSSED!! Ones with the rare decal patterns are worth finding a home for.