Found this in a box of parts...still looking for the rest of it. Can anyone tell me what I'm looking for.
The case back is engraved 01 0021 505.

I'll shoot some better images tomorrow when I have more light.

 

Zenith codes can be partially read as follow:

The first 2 digits are reference to the case material:
01 (stainless steel) which is pretty obvious here

The last 3 digits are reference to the movement:
505 is cal. ETA - ESA 9164 (tuning fork movement).
Rössler says that this movement was called Zenith Caliber 50.0 under licence from Bulova & Pat.

So I guess we are looking at Zenith XL-tronic's case:



Cheers,

Jeremie