On long term storage and protection of the barrels --

I've heard (first hand) from Indian gentlemen that they'd store them in barrels of oil - completely submerged in oil.

On 'vintage' vaseline, I've seen/handled 19th century vaseline jars (that hadn't seen daylight in ~100 years) that still had jelly in them. I actually have such a thing here in one of my rifle cases. The consistency of the petroleum grease is similar (same) as what we have today.
I'm sure that there were 'boutique' grades which claimed cleaner/clearer appearance or consistency, but the stuff is the same as what you get at the pharmacy nowadays.

Cheers
Tinker