The Beyerdynamic ‘Custom One Pro’ headphones let you replace the stock side plates for custom ones. Hence the name, possibly. Made these to have exagerated Left Right markings but the possibilities are endless. Feel free to use this model as a template to create your own designs!
Here are some examples of other designs I made in the past, but these files were lost a long time ago sadly.
https://imgur.com/a/j9ODG
The author hasn't provided the model origin yet.