I am the proud new caretaker of a 50 year old zodiac that looks like a chronograph model 4553 (based on purchase of access to historic catalogs, thanks Butch!) except it has pushers like models 4551, 4552, 4555, 4556, 4557, 4558 and so on.

The original owner, a buddy of mine, says that he purchased the watch in 1968 or so. Anyone have a definite model identification on this model?  See photos.

brent