Bought this in anticipation while I was looking for a Zeiss 18mm ZM. Ended up finding the lens bundled with a Zeiss finder...don't really need two 18mm finders. Quality-wise, the 2 finders are very similar.
Note, this is a 12mm Finder originally made for an Epson RD-1, which had a 1.5x crop factor. 12mm x 1.5 = 18mm voila. I've compared the frame-lines with the 18 ZM and a leica 18 and they match up, at least to my eye. The condition of this Finder is excellent, I mounted it a couple times but never actually used it outside of my house.
$225 net to me. A low price alternative to the Zeiss finder ($420 new) or Leica ($760). I have 100% positive feedback on ebay under the name dhuntsin. I have also bought a few items here.