This is a Singer
model 15. It was in production a very long time and were subject to improvements and a few alterations along the way. Around 1930 (maybe 1928) it was given a stitch length lever with reverse, this one can drop the feed dogs too. The other variants don't have this ability in general. Notice the difference in for the stitch length setting.
This is a 201, all of it's variants can lower the feed dogs. It's a nice machine.
Here's some info on the 99. Only the later one with stitch length lever has revers stitching. Mine is from 1934 and it has the stitch lenght knob. It's a nice machine and I can recommed it for anything but making jeans and jackets, hemming jeans is easy work on it, and I have made a shirt on it and it was a joy to work on. It all depends on what you want to do. You will manage on a 99, but my 201 has luxurious space under the harp for larger bulks of fabric. The advantage is it's smaller size, easier to move around (15s and 201s are heavy). It's very easy on the user, threading, drop-in bobbin case...
Model 66 is the full size verision of a 99, much the same machine but a bit more space for maneuvering larger pieces of fabric.
There are lots of other worthy models and brands well worth taking a chance when they turn up at the right price, but I will not confuse you any further. These are common machine, you will sooner or later bump into one if you keep an eye out. They are easy to get stitching again and pretty much indestructable.
Model 15 is a favorite among quilters, but that said, I have come across several who have set up a 201 for free motion quilting, one person free motion embroidery (with out a hoop). There's info on this on the web. I have manage to free motion on my 201, but I hardly do this type of work and I'm not the one who should give any advice
