Just an opinion here.
In the 'old days', it was common to mount large diodes vertically to save space on a PCB where space was at a premium.
It served a couple of functions. To save space on the board, to keep the diode up off the board for heat dissipation, and provide a rigid support for anti-vibration protection.
My guess is that's a 'special purpose' mount made for the instrument manufacturer specifically for a particular purpose in the instrument. A 'special order' item.
I've seen a lot of simpler mounts made for the same purpose in a lot of equipment. That one seems like a more elaborate configuration.
I don't think you're going to find another one like it made for mass-production and distribution by a manufacturer.