Hard without a photo, but my guess is that you have a re-edition Tag Heuer Monza or first re-edition Monaco from 1998/ 2000. Both of these are really Tags, but have no Tag Heuer markings on the watch- only Heuer. I believe that both these watches did have the marking "By Tag Heuer" on the back no reassure buyers that the company hadn't gone mad and reverted to Heuer branding ;).

The fact you say it has a buckle leads me to think that its a Monaco, as the Monza had a deployment strap only

This is a bit different from the true changeover watches from 1983-5 that had some Heuer labelled parts and some labelled as Tag Heuer- not because of any clever retro-based marketing plan, but because they just used the parts they had.

Reminds me of my Alfa GTV from 1971. Some cars had the Weber carburettor and others had Dellorto- most enthusiasts will tell you that the engines perform and sound quite different- which cars had which depended entirely on which was at the top of the pile when the guy reached into the crate!