A friend found this in an old barn on a farm that he bought. Solid with just surface rust. Cap unscrews easy and inside looks good. No oil inside maybe used for bringing gas to the farm. Value?

I'd pay $400 for a can like that. Others might pay a bit more.

Here's a few that sold... The one that sold for $200 was in 2018. I couldn't find a year for the one that sold for $495, however, I assume it was last year. There was one other in the same condition as yours that sold for $150, but that was in 2012.

Don't forget, auctions do not accurately portray the value of something, I just posted those for informational purposes.

I think Bustermonty's estimate is accurate. I'd say $350-425.

Hope this helps,
Steve