The serial number on mine is under the front slide plate. Here are pictures of the thread path, I hope you can see the red thread. I threaded the needle from L to R, and the hand wheel turns towards you, as with a Singer. Needle on mine has flat on the shank to the R, and it does look like a 20x1, although I would have to put a known 20x1 into the machine and try it to know for sure.
Let me know if I can help with anything else.