I have a 603 and a 600E. The 603 is a first generation machine, made in Anderson SC, an Auto-Reel that has a Touch & Sew label pinned onto the plastic faceplate as an afterthought. It has no plastic gears and runs beautifully. It was perfectly clean and well maintained before I found it.

The 600E is a true T&S, made in New Jersey. I haven't opened up the 600 to look for plastic gears on the bottom, because it is stuck and I am lazy. But I am pretty sure it doesn't have any. The only reason I am going to eventually get it going is because I have all of the chain stitch attatchments for it and the 603 doesn't chain stitch.

I've read that model 620 is the cut off for metal vs plastic gears. The plastic gears can be bought new and aren't terribly expensive if you get one with bad gears. I have a 648 with bad gears still waiting for me to make it a priority to get running.
Rodney

I have a 600E on craigslist right now. I bought it 2 years ago for the cabinet ;)
When I finally got the 404 switched out to the 600E cabinet, I finally cleaned it up and oiled it. HOLY SMOKES, that is one FAST machine :)

I do like Touch & Sews. They're descended from the 400 and 500 series slant needle machines like your 404. I do think the earlier machines are a bit superior to the Touch & Sews in terms of smoothness and speed though. At least my daughter's 401A is.
One thing about the Touch & Sews. I've said it numerous times (I like repeating myself). You need the owner's manual sitting next to the machine to get the full benefit from them. They're nice machines but they're not intuitive to operate.
Rodney