sells on cameraquest for $229...
urs for $150
works on all the bessa r2's, r3's, and r4's
Works smooth and has very little marks of use...
I can see how people can get 3 frames a second with it although I have never had the need to shoot so fast
for more info see:
IMG_1691 by Heespharm, on Flickr
IMG_1689 by Heespharm, on Flickr