I have a near-new 15mm Expanse that I am wanting to trade for a 6mm or 9mm version of same model. Has box and caps. This eyepiece is very sharp on-axis at f/6, and soft at the edges of its 66 Deg. AFOV.
HOWEVER, when "Barlowed", it is very sharp across the entire field and shows as much transmission as my 15mm Ultrascopic. Also, it is sharp across the entire field in a f/11.1 refractor. Obviously it is "f/ratio sensitive". A lot more eye relief than 15mm Plossls.
If no trade, would sell for $40 post-paid in CONUS.