What is this?

If you know what's the function of this item, please drop a note in the guestbook.

I received the following pictures with this text. Feel free to contact Darrol Davis who owns this piece.

"I have been collecting Canon F1 equipment since 1971. Recently I got an F1(old) prism that I have never seen before. 31/2 inches tall with a 3/8 view hole in front and a connector for power from the MF motor drive on the side. It powers up and produces a red dot that can be adjusted by a lever on the back near the top. Unit is all black with the Canon name on the front. Does anyone know what I have? Maybe medical or industrial use? I can provide photos."