6x17 90mm viewer

These are the model and the fusion360 source. It works quite ok…
It's a shell, overengineered and occupying a lot of space for a cheapo 0.45x optical addon. 

It's made for Velvia's 6x17!
https://www.printables.com/model/99364-open-6x12-6x17-and-6x24-panoramic-camera

amazon source:
https://www.amazon.it/dp/B08MW5VCNF?psc=1&ref=ppx_yo2ov_dt_b_product_details