This is a potentiometer holder for the MK arcade PCB. I consolized the board with a Highflow.nl Midway Y-Unit acrylic case that came without this part.
A metal mounting bracket is offered by Marco Specialties https://www.marcospecialties.com/pinball-parts/01-6858 but international shipping is overkill, hence here is a free design for the lucky owners of a 3D printer !
It's designed for M3 steel stands, please choose their size according to your potentiometer depth and its desired position.
The author hasn't provided the model origin yet.