HunchBluntley: The offline "backup" installers for most any game that's been added or updated in the past couple years (at least)
should show the version number to the right of the filename in your library viewed via a regular browser; no idea about Galaxy.
p1881: - Fallout 1/2 Classic show no version
- KKND2 shows no version
- etc.
The installer all have versions when I download them, so I reckon it can't be hard to have that version also show in the download section.
Those are very old titles that haven't seen developer updates since before GOG existed; that's why I specified "most any game
that's been added or updated in the past couple years (at least)". ;) (If memory serves, GOG didn't used to have in-game version numbers visible for ANY games, even in the library -- they only showed their internal version numbers related to how often they had updated the installers.)
I'm sure some people who have any of those titles could tell you what version numbers they are at. You should also check those game series' forums here to see if the info is already posted.