Exactly, they're plates to follow using a pantograph machine that will in turn engrave your piece. I love the "Himalaya" type in the article, very Art Deco.

If you want a demo of a vintage one, this video from Inheritance Machining [1] is a great watch. It also shows how you can change the scale by adjusting the lever arm positions.

[1]: https://www.youtube.com/watch?v=7am-ysvGD3s