New toy! Shop built press brake, missing a piece or two?

Just got my new toy off the trailer Saturday. Its a press brake that a local outfit built before closing their doors. I bought it from a guy who bought it from them. Got around to messing with it a bit today and, to my novice eye, it would appear that I'm missing a piece(s)? In the pics you'll see the thick plate with the trapezoid looking notches top and bottom has four threaded holes and four open holes. The threaded holes are for attaching the plate thats sitting next to it, resembling an I-beam. I know these two pieces go onto the top, movable section of the press and holds the top die, but I dont see how exactly. Theres also four pairs of holes in the movable section that go all the way through, I'm assuming they play a part in this. I googled pictures of different presses hoping one would resemble this one but no luck. Fingers crossed that you guys can school me here.

Its definitely shop built, the plate with the two opposing dove tails are generally mounted on the lower and then the lower die holder sets/bolts into it. The dove tail grooves allow the use of adjustable stops to allow repetitive forming or some type of fixturing.
The other item is a die extension also generally mounted on the bottom as well, however on this machine it looks like it my have been mounted to the upper Ram either way it's most likely 1/2" wide and a little deeper then 1/2". This would allow the upper die to set into it and then lock into place by Some type of set screws. Near as I can tell from your pictures is that the upper die holder was mounted some how through the use of those through holes. The main thing to remember with this type of press(single ram) is that you must always press/form from the center out in both directions.in other words if you were to press 10" wide material then you would place the center of the material to be formed/pressed directly under the hydraulic ram with 5 inches on either side of the dead center of the ram, if not the upper ram bed could cock sideways.