- have the movement serviced
- have the case and pushers cleaned
- have the plexi polished or replaced with original

I wouldn't:

- have the dial touched
- have it relumed
- have the case polished or refinished

The second gen Autavias have a specific bezel to the model (the "Siffert" is actually an 1163 T, for example. Heuer no more called the watch a Siffert than Ferrari called the 365 GTB/4 a Daytona), but we assume that customers were able to request a different bezel when ordering the watch, or potentially when buying at a retailer, if they had appropriate stock and the staff to switch them. In the previous generation of Carrera, for instance, they offered tachy, pulso and deci dials - it's one thing to commit to a dial, but another for a changeable part like a rotating bezel.

Imagine you're an engineer, and you fancy one of those white-dialled Autavias. But what use are you going to have for that tachymeter scale? You can do the mental arithmetic to calculate your speed and it's there on the speedp in any case (ignore the fact that you might just be OCD enough to want to calibrate your speedo!). But a deci scale? You could use that at work. So you ask the retailer nicely if you could have a deci bezel instead and, lo and behold, they have one! So now you have a Deci Siffert and can proudly wear it to work... or leave it in a drawer for 25 years, should you prefer!