Case material of a 70s UG Pocket watch. 542134-06T

I'm trying to find out what case material is of one of my UG pocket watches. I believe they it is a 542134-06T but I cant tell for sure as it still has its sticker on the back. The reason I believe it is this ref is that I also have another seemingly identical one that came with the paperwork all filled out and the sticker taken off.



Both of them have these two makings on the back of the case; a number 20 and a "C" in an oval that is in a rectangle.



Would I correct in assuming this means that they are 20k gold plated? The reason I am asking is that they are heavier than a steel one I have by about 10% (Steel 28g to 31g for the gold one). Also, going by this thread (https://omegaforums.net/threads/universal-genève-information.66405/) ref numbers beginning with a 5 are 14k gold or does that logic only apply to ref numbers with 5 digits?

Your watch was produced after the nomenclature change (in the mid 60's).

In that case a watch with ref 542xxx means that is a gold capped watch (5 as first digit) with cal 42 inside (second and third digit)

Brilliant thanks. Gold capping had slipped my mind. Would it be 20k gold capped due to the "20" in the stamp mark?