[Doxin]

Roughly no one already says GSM. When talking about paper you'll hear people say things like "That's a sheet of 120 gram"

GSM basically only ever appears in print. If someone DOES ask "what does 120 gram mean here?" the clarification is going to be "Oh that's grams per square meter" and not "Oh that's gee es em"

I should mention GSM is also probably an americanism. I'm in the EU and out of the five packs of different kinds of art paper four are labeled in g/m2, and one has no labeled weight at all. None of them are marked in GSM as that abbreviation only works in english, while g/m2 works in all languages.

[roryirvine]

In the UK, "gee es em" was the usual term I heard at the local paper merchants when I was a regular customer in the late 90s - early 2000s.

Of the four reams of paper/card I have at home, two are labelled in "gsm", one is "g.m⁻²", and one uses both "g/m²" and "gsm" in different places. Weirdly, it seems that the specialist stuff is more likely to use "gsm" than the everyday 80 g/m² A4.

[Doxin]

I guess the fact that over here GSM was also the term for a mobile phone for the longest time has affected things some.