Balance Parts

I can't ID what you have based on the stamps alone. They aren't product codes or anything, they just indicates the strength of the spring. I would also double check the one you say is labelled "55 3." That indicates a 56" long balance which is HUGE. Way larger than anything you usually see.

Otherwise, 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. The video below will go into more detail.