Speedmaster 145.012

It’s important to differentiate between age/damage/wear to case or cosmetic parts and the movement. Although they often go hand in hand that’s not always the case and you can have a decent looking example with a poor movement. Equally you can have a well worn, case and knackered dial with a decent movement.

For example, water ingress is an issue that will often lead to issues with both the dial and movement. However, the dial could be damaged by improper storage, careless removal of hands, a damaged crystal etc, which wouldn’t necessarily impact the movement.

Regardless of whether you’re looking at the lower end of the market in terms of case/dial/bezel or movement condition, I’d say it’s generally false economy. Parts are more expansive individually than as part of a whole watch. When buying a resto project you’ll often spend more than it would have cost to simply buy a good example in the first place, with the added kicker that the parts often wont sit well together due to differing wear/patina.
Of course this isn’t always true. It’s possible to buy watches that look poor to a lay person, but clean up wonderfully. The typical example is a filthy watch with a scratched and cracked crystal, hiding an unpolished case and a good dial and movement. This is how I like to search for watches. There’s a skill in doing this though and you have to develop an eye for it. Otherwise you end up back to category 1, a crapped out watch with a dull and damaged dial that requires more spending on it than it’s worth and ultimately doesn’t give you any joy.

TLDR: as long as the movements in decent condition and not overly worn, rusted or missing parts, it’s my experience 321’s can be serviced adequately. Other parts such as the case and dial may end up costing you a fortune if they’re also poor. Generally buy a good example to begin with.