Wow, I own a WT-800 I just bought off of these forums in August that was manufactured the on the same day (8-15-03.) Mine has a serial number that is 3 higher than that one (1059)
Interesting that these both have gone up for sale on this forum in less than 2 months.
Also, for the technically inclined, this is a WT-800A, revision E model. It has the NL-4 outputs for the Bridged out, instead of the banana clip outputs, but is functionally a normal WT-800A besides that. So 400 watts per side at 4 ohms, 800 bridged at 8ohms.