So, it was a 286? Wow. They sure did some different ones with the 2500 series. I'm also looking for the proprietary extra 256K ZIP VRAM for my 2500 SX/20 (which is a 386SX). Let me know if you find them. The tech specs mention nothing about what they're supposed to be, and my attempts to buy some on eBay resulted in failure (they were likely the wrong ones.)
I did put Windows 3.1 with the Tandy Sound driver on mine. The Tandy Sound Driver works pretty awesome and is the only vestige left of the T1000 on the unit.