This is the Artist model of the King 3-valve bell-front euphonium. The photos don't show it clearly, but I think it was a satin finish (now smoother, probably) and a gold-wash bell interior (really can't tell, and seller doesn't say). Here's why I think it may be a bargain: it is listed as a tuba, and the seller says it needs TLC. But I don't see a lot to worry about for condition. There appears to have been a repair around the main tuning slide - I see some grunge beneath it, but I can't think that would be much trouble. And there some very small dents I would ignore and a little larger crease at mid-bell that should an easy fix. As far as I can see from the serial number, it seems to have been made in the 1950's. I think it's easily worth a few hundred more, but it may not go that high.
ITEM HAS SOLD FOR $172!!!
Current bid is $89.89 and I see no mention of a reserve.
http://www.ebay.com/itm/VINTAGE-KING-TUBA-625-MODEL-NO-1-938527-SILVER-PLATE-WITH-YELLOW-BRASS-FRONT-/201361194868