The early smooth finishes with homogeneous particle size were prone to "brassing", where the PVD coating wears at the edges revealing the base metal underneath. Examples of Heuers with this type of finish are the 510.511 Carrera (though this was a later attempt at perfecting the smooth finish, it is often still the victim of brassing) and the early Monzas. From photos, it looks like the PVD Monaco does too but it really needs handling of the watch to discern properly.

One solution tried was to include a mix of particle sizes, shown by a rougher finish of the PVD with larger particles readily evident. Ref the 110.571 Carrera, the Pasadena and later Monacos. The solution wasn't perfect - some brassing still occurs and the larger particles can also chip and leave the watch with a pockmarked appearance.

Heuer, and others, were experimenting with their PVD finishes pretty much constantly, so there can be considerable variation between the original PVD finishes within a model range over a number of years. They seemed to go back and forward between the "smooth" and "lumpy" finishes too - I guess each has it plusses and minusses.

Modern PVD finishes tend to be of a homogeneous particle size but often thicker than their predecessors - certainly, adhesion and resistance to brassing seems to have improved over the years. It's an interesting topic, and good for us that Heuer were amongst the pioneers of this finish - for me, it often makes for an attractive watch.