: The others were made by Heuer under the different brand names,
: Glycine is a fully fledged swiss watch maker on their owns so
: why would they get heuer to make it for them....

Clebar etc were watch makers too. There are a number of occasions where a watch house has filled out its range with a rebadged model from another manufacturer, usually in a model that's not in their usual range of expertise. For example, the early Heuer divers are manufactured by Monnin in France, but are still badged as Heuers.

I agree that this Glycine looks pretty much identical to the triple calendars Heuer was making, and being sold by various watch houses (including themselves), so the possibility has to be there. Jeff's suggestion of comparing the serial numbers is a good one.