Mamiya RZ67 PRO II Fine Focus Gear
Version PRO II of the RZ67 features a delicate fine-focus knob that operates through a gear reducer (this one). It is quite fragile and prone to breaking easily, resulting in a grinding sensation while adjusting the camera's focus.
This serves as a replacement for the gear. Printed at the highest quality settings supported by your printer, I used PLA and the "0.08mm Extra Fine" preset on Bambu X1C.