Hi everyone. I've been working on sewing machines for about 30 years, and have had a few of these 120's. They are some of the strangest sewing machines I have ever used. Strange because they implicitly instruct the owner to never oil the machine, yet if it isn't oiled, it will quit running. PLUS, as Joe mentioned, there are actual oil ports on the motor, which means, IT NEEDS TO BE OILED!! That slays me.
As far as I can tell, these were semi-bottom of the barrel sewing machines. They were fairly inexpensive and made almost as throw-away machines. They have a stitch length adjustment, using a really strange side to side lever system that no one else has ever employed. You can open the case to get beneath the machine and drop the feed dogs by sliding a nylon bushing out of the way. Not a very practical way to do that, but it works. It is just difficult to imagine a machine like this, that has virtually zero maintenance, and then they expect you to lift the entire machine up so you can fumble around with a difficult to move nylon cam to drop the dogs. Weird.
Taking everything into consideration, Joe is also probably right about Sears wanting this machine to seize up so that you buy a different one. Since it isn't supposed to be oiled, it isn't user friendly, and you either have to take it in to a Sears store, where they will oil it up, or get a new one. Sears wins both ways financially on this machine through service or selling a new machine.
Every one I had, and I have one sitting next to me as I write this, every one I had ran like a tank. Yes, the stitches were good, but if a metal machine can be said to be cheap, this would be it. But hey, this is a no muss, no fuss sewing machine that will literally work until it doesn't, and then you are stuck with it after that.