Got a set of very good condition B5 S4 front calipers.
These are the half steel, half alloy version used on the facelift cars, though they will fit earlier ones as well.
I dont know how old they are, as they've come off a car i'm breaking, but they are in extremely good nick, and looking at the pistons and overall condition they cant be any more than a year or two old. All pistons and sliders are free.
These calipers are standard fit on a few Audi models including various A6 and A8's, and can also be used on B6/B7/C5 etc as an upgrade on lower spec cars.