On modern TAGs, the X would indicate a prototype. Not sure on these old ones, but it is a little odd that it has a Heuer on the caseback and TAG Heuer on the dial.
I think this was a Heuer 2000 that was redialed as a TAG when the company changed names. My two tone 3000 had a Heuer backplate and clasp but a TAG dial. I think they were just trying to stay afloat and doing the bare minimum necessary. On the other hand the X is weird, and if it was a prototype why would it have -1 on it?
There is here another 266.006-1 with Heuer logo on the caseback, TAG Heuer logo on the dial, and also the X… maybe the X was included when the TAG Heuer logo is on the dial instead of the Heuer logo?
I never noticed the cross. It seems it was only used on the 266.006-1 version. There are several to be found.
I myself have 2000 and 3000 watches that also have Heuer lids on watches with TH dials. This was common in the late 1980s.
I think this also happened with buttons.
There is here another 266.006-1 with Heuer logo on the caseback, TAG Heuer logo on the dial, and also the X… maybe the X was included when the TAG Heuer logo is on the dial instead of the Heuer logo?
I wish she was a little prettier, but not such a bad looker either. Crystal will need a polish and gotta add a gold bracelet.
Just to be in full Ken mode.