Searching for 368-72

I'm not sure what you have, unfortunately. That stamp isn't a product code or anything, it usually just indicates the strength of the spring; that said, you have a very peculiar stamp indeed and I don't really know what it might represent.

Let's start with the basics and work from there. In order to figure out what Series this is, I need you to remove an undamaged version of this balance from the window and show me clear pictures of the top and bottom nylon fittings. I will also need to know the dimensions of these fittings.