Ever since Cambo has been manufacturing studio stands many photographers ordered these with an accessory tray. Just to have things like the exposure meter and Polaroid cassette at hand.
At some point, the screen near the camera replaced the loupe and Polaroid. Looking at the DB, this one must be about 25 years old by now.
For use on our M-Line (Mono and MBX) of studio stands we’ve got the Mono-52. The U-52 is the notebook tray for the U-Stands (UST and UBS). Use is limited to the UBA cross arm, which slides on roller bearings. The U-4 requires a different solution, due to its crank.
That solution is called CT-460. It can be used on a C-stand, or – attached to a U-9 or U-29 – at the studio stand’s cross arm.