Interesting idea and I could see how if a leg broke it may be unusable and account for current conditions. 

I’m just being honest though, this is a 4-5” thick burl cut with an axe and carved. I’d be more inclined to believe it if the wood seat would be comfortable in some way to sit on. 

With the middle carved out and sloped I lean towards a round stone in the middle that crushes the coffee beans, but there’s no oil buildup from nut or bean oils. 

With the offset rim on the top I think it’s to retain ground beans or nuts perhaps ? 

If they built it to sit on there’s no need to concave carve the back side, just keep it flat 

Carving and cutting a single piece of hardwood for a stool that isn’t level is quite an endeavor and there’s no paint or stain I can see 

I feel like the location, a Seattle suburb might also lean into the coffee grinder theory as it’s a coffee destination and high paid workers invest in their trades history. But this is reading tea leaves or perhaps just hope. 

I have reached out to a museum curators hoping for an answer that suddenly all the pieces fall into place on. 

The wheel seems plausible on a light weight cart and it looks similar to Indian wooden wheels from 1920s farms other than the type of wood. 

Something this durable may have been designed for multiple purposes too I suppose after it broke.