Really old gun oil

[Scottrt]

My most recent acquisition was obviously put away well oiled. But that was long enough ago that it was now like dried shellac. Everything was either very stiff or stuck, Including the grips to the frame. 90 minutes with some solvent and a toothbrush cleaned everything nicely, and some fresh oil has it working beautifully. Not a speck of rust so I guess it worked. It wasn't thick or greasy enough to be cosmoline.

Question...Any guesses on how long it was in storage for the oil to get that dried/stiff? (assuming it was in the house in proper temperature and humidity)
The gun has light holster wear, but did not come in or with a holster

This isn't a quiz ...I don't have an answer...But I know many of you have so much collector experience in your lifetime, that perhaps you would a hazard a guesstimate...?

Curious....Scott