From: David Woyciesjes
<DAW(a)yalepress3.unipress.yale.edu>
  Date: Mon, 8 Oct 2001 16:49:55 -0400
  I have a Unisys 486 computer. It's a SX-25, with a DX-50 in it also.
  It's mfg date is 10/92, and style number is SG-3102-425. It's
"plateau" is
  labelled Evaluation Unit A. That would explain the XXXX in the FCC ID
  field...
  On the motherboard itself, it has a sticker with...
  43611896-000
  PW300  486SX/25
  9240      AVEX 
Sounds like a 486SX/25 system upgraded to a DX2/50 with an OverDrive chip. 
 
Or somebody stuck in a DX-50 and its just running at 25 MHz.