This models, are credit card big and 5 mm tall test samples you can stack on each other and turn. This design allow not only to see the print surface, but also (5mm) of layers.
You can emboss the filament type/ material on the side to see quickly what type it is (PLA, ASA, PETG, …. customazible ;) )
Futher you can choose a model with print temperature and hot bed temperature. Further there is space for two printed lines (name? vendor? prize?…) Or you can just print a blank and make hand notes on the model.
For manufactures, there is enough space to add your logo, or further descriptions.
And for the creative ones, you can modify it to make a liddle overhang or tolerance test. There are planty of possibilities. As long as it has the same nob connector to attach to the upper sample, and has got the hole for another sample to latch on, its fine.
There is also the possibility to print a hole for string attachment, but I personally don\t like it, because it would need a liddle bit of support :/
The author hasn't provided the model origin yet.