I've been lusting after an old Singer for quite a while--just to have one. It's not like I need any more sewing machines. But I saw this on eBay for a decent price and swooped in and bought it.
It's a 15-90. The fun thing about old Singers is that you can look up the serial number and see when and where it was made. This one was born June 6, 1946, in Jersey, exactly two years after D-Day. It's a Baby Boomer machine!
This is what sold me on it: the scrollwork faceplate. So cool.
Sister machines to the 15-90 are the 15-88 and the 15-91. The 15-91 has a "potted" motor and is gear driven. You see this model the most on eBay. I've read that the gears are fairly fragile, so beware if you plan on sewing thick denim, I guess. The 15-88 is for treadle-use only.
And the 15-90, as you can see, is belt driven. You can also use it as a treadle or handcrank machine.
This has a vertical oscillating hook. It's my understanding that this kind of hook is less finicky about thread size so you can run heavier threads no probs. I still need to clean and oil this machine before I really see what this can do. Though it does make stitches. I tested that. And it makes a very nice reverse stitch, which is always nice.
This machine is pretty similar to the Singer 99 (another ubiquitous eBay machine), but the 99 has a horizontal rotary hook and different bobbin. And the 99's tension knob is on the front, not the side.
It's also kinda like the 221 featherweight (the machine I learned on), but the 221 has a rotary hook and smaller bobbin...and is portable.
If you're in the market for one of these you can usually get one for under a hundred bucks, unless it's a rare one or something. But they made like a trillion of these so they should be pretty cheap. This one was from a batch of 250,000. I think they pop up on eBay in waves...probably depending on garage sale season.
People do sell these on eBay for $200+ as industrial strength leather machines, which is sorta a scam. They will sew soft apparel leather and they are really tough little machines, but in no way are they true leather machines. If you're in the market for a leather machine, take a peek at Leatherworkers.net and see what's out there...or just buy a Juki 441 clone and call it a day.
Other old Singers that I haven't mentioned that would make good beginner/general-use machines: the 201 and the 66 (the full-size 99), and probably a handful of others that I don't know about.
I just remembered that Sailrite used to offer a basic canvas machine years ago...
Looks a lot like the 15-90.