That one has an old SN. The SN on mine is 497, and it's the older model Valhalla. Anyone interested and new to tube amps, be sure to ask the guy how long he thinks the tubes have run for. A replacement set will cost you $40; not much of a savings over new, to be honest..
PS: If I'm not mistaken, the newer models are slightly more efficient (40W vs 45W).