If you would like to see some photos of this "hinge" plate check out this post on the Forestry Forum/Timber framing section:
http://www.forestryforum.com/cgi-bin/board/YaBB.pl?board=tframe;action=display;num=1060266331
There are a couple of photos of this hinge there, which I took. Also check out the schools photos of the barn raising at:
http://www.mountainschool.org/program/barnchrono.htm
At the time I posted the photo of the "hinge" plate, I didn't know who designed or invented them. But Emmett was there and has told us that it was Ed Levin the frame's designer.
I'm not sure how deep the bolts go into the concrete but there were some drawings that showed "J" shaped bolts embedded in the concrete for hold-downs of other sill boards. Jim

Whatever you do, have fun doing it!