Ideas on opening this container. Mystery treasure inside?

I purchased this Chinese barrel type vessel recently. It was sold with the description stating there were unknown contents. The consignor and auction house were unable to open it. It came from a high end auction house that handles really good estates. I don’t think they ever would have sold this piece if it wasn’t for the mystery contents. I was the sucker that took the bait and bought it. There is something reasonably heavy and solid in it and possibly some smaller things. I assume the auction house tried relatively persistently to open it, although I see no damage or signs of forced entry. Even a butter knife is too thick to fit in the space between what I believe is the top and the rest of the barrel. I got it to twist like half a centimeter maybe but no more movement. It’s hard to grip without damaging the brass trim. I tired sticking it in the refrigerator for a couple days. I was hoping maybe the wood had swollen over the humid summer and fall and sealed itself. My thought was that the wood contracting might undo this. I guess I could try the opposite too. The barrel itself can’t be worth much so it might be worth destroying it to get it open. I’d obviously like to avoid this if possible though. Any thoughts on a method that might work? It’s around 6” tall.

 

Dag-I've got a couple of those (6" tall) and i always thought they were spice containers.
They're frequently chipped,dinged or cracked-perhaps because the wood was correctly seasoned (?).

 

OOOOH, that's intriguing!!! I'm still betting it's just VERY stuck!!! Did you put a magnifier on that line to see if it's actually a lid!!! Then I'm not sure what my next step would be to get it open and not damage it!!!

 

Try a metal spatula, carving knives, gently work into the opening, now do the same to the opposite side, work your way around in this manner. As it opens use two tools to open it a bit more, and so on, prying slightly as you go.

Do not add any type of lubricant. It will swell the wood.

After it's open get some sand paper adjust the fit.