How is this thing called?

[I14R10]

It's somewhat funny question, but here it goes.
You can find them on HAM radios - it's like a variable capacitor for tuning, but it can be rotated as much as you want. It's used for setting the frequency on digital radios. It just keeps on rotating, doesn't even stop on 360 degrees, you can make as much turns as you want.

 

[Dan Mills]

Probably an 'incremental encoder', good ones are optical, cheap ones use contacts.

ALPS, BOURNS & AVAGO (Formerly HP) are the usual suspects as manufacturers, there are others.

Regards, Dan.

 

[I14R10]

That's it, thank you!!