This is a NICE Conn 20L, made in 1969. Condition is really fine; hard case is included. Buy-it-now price is $599 and there is a make-offer button. Shipping is only $41.18 from a top-rated seller. Of the 3 valve horns that have shown up lately, this is the one I would personally jump for (it's a personal preference, but I have played horns of this era when there were still new).
ITEM SOLD FOR $599 - CONGRATS ON GETTING A CLASSIC HORN!
http://www.ebay.com/itm/CONN-Euphonium-Silver-20L-1969-M60445-/372013924227