Hi, thx ! And yes, it does have the correct mechanism fited. It lacked some essential parts when I bought it but the movement was running strong and smoothly (as a regular automatic) and the dial, hands and the watch itself were in a fantastic condition. Via a good friend (and former Rolex watchmaker) I got the ref 6556 repaired and serviced in its original condition. Unfortunately, those parts are so rare, I guess finding them again will be a real quest. As rare as they are, would you believe my cousin has another example (now also with correct trubeat mechanism) which used to be his father's watch. Will make a picture of the two of them next to each other for a real rare view..
Imho these interesting pieces deserve much more attention then they get. But I guess being a quartz-lookalike does not do these watches any good....