It does look unique, doesn't it?
Every finder I've ever seen (and then some) for the Hasselblad is shown here:
http://www.photoethnography.com/ClassicCameras/index-frameset.html?HasselbladFinders.html~mainFrame.
It looks like the 203S finder is different from all of those. Funny thing is, the one in the 203S picture looks vaguely familiar to me, but I can't place it... Senility must be setting in!
I'll keep poking around. I'm curious!
One other difference between the 203FE and the 203S is apparently different lubrications were used on space cameras--my former NASA employee friend tells me that the regular oils evaporate in space and make a mess of the camera. Since I'm not planning to leave the Earth anytime soon, just the modified winder should be fine for my needs.