Original WT400 (not "upgraded to WT400 specs", this started its life as a WT400).
This has been my gigging amp since I bought it new in the late 90's. Anyone who knows these amps can tell you why. I'll regret this the moment it's gone.
Disclosures - the bag is old; the amp has the standard scratches you'd expect on a well-gigged head this age. The DI level control on the back took a bang many years ago and has a cracked knob and slightly bent shaft (see pic 2 - not a big deal). Still a solid-every-day workhorse. As far as audio issues, none [well - this head can tend to be "hissy" when there's no patch cord plugged into it, so if you're planning to buy it to use without a bass plugged into it...

]
$400 shipped to CONUS or Canada.
[I'm kinda set for bass gear in this price range - not much would interest me UNLESS you happen to have a Berg HT112ER...]