Parts for an antique stereoviewer (Holmes, Keystone, etc), containing a iPhone 13-Pro-Max Holder and a Tripod Mount for the stereoviewer.
Take a look at https://www.stereoscope.nl
Print the Tripod Mount to mount a Holmes viewer to a Tripod.
Print the iPhone 13 Pro-Max Holder to attach your iPhone to a Holes viewer.
You can print the Holder Bolt to fasten the Tripod Mount or to fasten the iPhone Holder to your stereoviewer (print two times if you need to fasten both).
The author hasn't provided the model origin yet.