...except that it's mounted on a lensboard, pointing *into* the camera body? Doesn't look graflok to me.
How is this meant to work? Do you have a third standard behind the film plane, with the camera pointing at the ground glass?
Its a sinar lensboard, The newer models (F P X) all have a universal standard system accepting boards/bellows/backs/attachemnts, via the same standard square connection. Its pretty smart actually.
I guess in this case it is mounted on the rear standard instead of the graflock back.
In some way it reminds me of a remote controlled 35mm SLR with a tube videocamera taking the image presented in the eyesight.
But also of an apparatus for eye fundus photography where a CCD-camera was fitted to a custom finder of a 35mm SLR, and used as only means to watch the finder image. The groundglass had been substituted by a field lens.