The Breitling Navitimer is the pilot chronograph with a slide-rule bezel. The bezel is the part people recognize, and it is also the part that gets replaced when the printing wears off. This note is about a used watch, not about buying one.
How it differs
A Chronomat is a different Breitling. The Navitimer bezel is a calculator, with a logarithmic scale, not a plain dive ring and not a rider-tab bezel. The dial has three subdials. The case is wide, and the crystal has to clear the chronograph hands. If the hands look crowded, look from the side before you decide they are bent.
Some examples are on a bracelet and some are on a strap. End links matter only on the bracelet. A strap watch still has lugs, and the spring bars should sit in the holes, not on top of them.
Common mods
People change the bracelet, the bezel, and sometimes the crystal. A bracelet end link that does not follow the case will leave a wedge of light at the lug. A slide-rule bezel that was fitted later may sit high or may not turn evenly. The crystal, if it was replaced, should meet the bezel without a lip you can catch with a nail. Chronograph hands are a movement concern: after a service, start the timer and see whether the center hand returns to zero.
What to check on a used piece
On a used Breitling Navitimer, check the bracelet end links where they meet the case, the crystal over the dial, and the movement. Read the slide rule at the 12. The zero of the scale should agree with the bezel triangle. If it does not, the insert or the bezel was disturbed.
The notes for those parts are the bracelet, the case, and the movement.