I'm repositioning this post in the hope that more people will see it. It is buried on the fourth page of an older "sticky" thread (whatever that means) and I haven't received any responses. I hope that its OK to do this.
I acquired these 9x12cm plate holders in order to obtain the film sheaths that were inside them. Although not quite up to the standards of Zeiss or ICA, these double sided holders are nevertheless precision built and have similar design features. They won't fit into any of my cameras. The larger model measures 111 x 167 x 15mm. The smaller is 111 x 158 x 12mm. Both have a 2mm wide lip along each long side. Both have small notches in the valley between the sides, to receive a locking pin on the camera body. Each dark slide is locked in place by a spring type mechanism that is squeezed to release it. The dark slides on the smaller model have metal "tongues" that fit into notches in the holder body. On the larger model two screws with round heads protrude from the body. The holders have metal handles with rectangular cut outs that "catch" the screw heads. Squeezing the handle releases it. Can anyone help to identify these holders?