yep, and you did not mention either the thermistor or the heater cartridge in your original post.

Just the extruder, not the hot end.

As for what the extruder is.
I doubt it has an official designation, it's the cheapest bit of junk I've ever seen.
But works surprisingly well, and I'm againt changing anything that works.

It's the only extruder I've ever seen that isn't spring loaded.

See what I'd probably do if I were to change it, would be to print a different carriage to mount the new one on, with one of my other printers.
But with it being your only printer - you're a bit stuck in that respect.

if you design something to match an extruder you actually have, I can print one off for you and post it.