1.
Indeed, I don't find either where is it used.
If I'm not mistaken, it's never used in SQ3.
So, why is it there?
Sierra had a framework of scripts, that each game copied, and started development from there.
Parallel to the game developments, that framework was developed and modified.
This file is part of the framework.
You can see a 'snapshot' of the framework, at some specific time, at
https://github.com/OmerMor/SCI16We see there this very file:
https://github.com/OmerMor/SCI16/blob/master/SYSTEM/GAUGE.SCAnd inside, there's explanation what's its purpose:
;;;; A class to display a thermometer-like gauge in a Dialog, allowing
;;;; the user to set a value.
2.
If you want to better understand the scripts, I hope you're using EricOakford's great decompilation:
https://github.com/EricOakford/SCI-Decompilation-ArchiveIt also has this file, with comments (based on the SCI16 framework...) :
https://github.com/EricOakford/SCI-Decompilation-Archive/blob/master/sq3/src/Gauge.scThis time, these both resources gave you the same answer, but in future questions you'll have, maybe they will have different information, so, it's better to check both. (I usually use EricOakford's decompilation, and check the SCI16 framework only if I feel that 'something is missing')
3.
Anyway, why do you care? :-)
It's quicker to just translate these few lines.
That's we did.
Until now, I haven't even noticed that this script isn't used in the game.