Recently, I bought three pretty old large format cameras and now, I try to find out, how to use them.

The smallest one ( 4 3/4 x 6 1/2 inch ) is complete, but on the middle one, the plate holders are missing ( so I don't know the exact format ) and on the largest one ( 10 x 12 inch ), there is no lens. As it might be pretty hard to find plate holders for the middle one, I am more interested in using the biggest and thought about a possibility to mount the lens from the middle camera on it.

The middle one came with a Carl Zeiss Tessar 21cm F:4.5, which seems to have a 6 cm screw mount. The largest camera has the same mount, but the diameter is 8.5 cm.

Are there any adapters ? Is the Tessar lens suitable for 10 x 12 inch as well ?

Here is a picture of the middle sized camera and the Tessar lens mounted. The largest camera does look exactly the same, just bigger.

Any ideas much appreciated,