Ah, hello everyone! Thanks to @DonRoPL for reminding me of this CS and sorry to @HikeAndMap for not getting back to your question.

The combos I meant were:

- fire_hydrant:model=*
- fire_hydrant:manufacturer=*
- fire_hydrant:year=*

Those are not commonly used and not part of the wiki article. I would suggest

- model=*
- manufacturer=*
- start_date=* (https://wiki.openstreetmap.org/wiki/Key:start_date)

Also I would suggest not to use the source=* tag on the object itself. This is nowadays done via the changeset (as you did).

When you name the source in your changeset, make sure you do not use any sources that are not allowed for use in OSM (e.g. Facebook like in this example).

All the best!