Adjustment of OT Antique Pine Desk Chair

Hello!

As of yesterday, I am the proud owner of an Ethan Allen solid wood antique pine Old Tavern finish swivel desk chair. It is item number 12-9530 from their catalog. It goes perfectly with the OT rolltop desk I found a few months ago.

My question is: does anyone know how to adjust the height? I see a collar on the bottom that has some kind of set screw. I turned it upside down and rotated the collar, both with the set screw in place and backed out, but the legs just spin on their pedestal and the chair doesn't raise or lower.

I'm probably missing something obvious, so thanks in advance for any advice. Oh, the previous owner didn't remember how to adjust it, as it had been several years since he'd used it. Though he thought it may have something to do with the set screw.

Nancy

I'd contact EA. Or, there's one listed on eBay; you could email the seller.