Thanks for contacting us! I hope I can help.
Before we begin, I'd like to briefly go over how these balances are categorized. Since you have multiple different windows I think this will help you in the long run.
There are three major details that go into identifying this kind of channel balance:
1) The length of the metal channel, not counting the nylon attachments on either end.
2) The stamp printed on the metal channel. This is not a part number or identification number of any kind, but is instead simply a code indicative of how strong the spring is. For example, I can tell from your stamp of "2510" that your two balances can hold a window sash weighing 5 through 9 pounds. Now, the logic of how the numbers of the stamp correspond to the actual weight is a little arbitrary, and not all that important, but I'll go deeper into it if you'd like.
3) The nylon attachments on either end of the balance. These are what dictate the balance Series, as we define it. These nylon attachments act as guides that help the balance slide up and down in the window channel where they install, as well as helping the balance interact with the sash when you open and close it.
Now, with all that in mind, let's look at the balance in your first set of pictures. You said that the length is 26" long, so that step is taken care of already. The stamp also reads as 2510, so when you're prompted to select your balance's stamp option, that's what you want to go with. As for the nylon attachments, I'll have to eyeball them. Based on how they're designed I think they match our
19-005 (top) and
15-001 (bottom). You can go over our pictures and dimensions to confirm but I'm confident they'll be a match just based on experience. If they match then you would have our
Series 395 channel balance.
Altogether, that would make this an
S395-26 balance with a 2510 stamp option. This is how all channel balances of this type are identified in a nutshell.
Let's get to the hard part: you mention that the balances are missing from some of your windows and that many of these windows are totally different sizes. This can get pretty involved, and in the case of the missing balances it will be especially tricky. Ignoring the size of the windows for the moment, are all of them identical in design? That is to say, are they all Viking windows? If they are then I think it would be safe to assume that all of them would be the
Series 395 channel balance (to reiterate, these come with the
19-005 top and
15-001 bottom attachments).
So we can assume the Series, but what about the length and the stamp option? This is where I'll need to give you some homework. In order for us to calculate the length of the missing balances I will need you to give me the height of the
visible glass. Not the overall height of the sash, just the visible glass as it sits in the frame. With that, I'm confident we can determine how long the channel balance should be.
As for the stamp, it's simply a matter of reversing the process. I mentioned before how the 2510 stamp indicates support for sashes weighing 5 through 9 pounds. Well, for the sashes that are missing their balances, you'd just need to weigh your sash on a scale. Any common bathroom scale will do. Knowing its exact weight will allow us to know right away what option would be best.
Hopefully this information helps. If you need me to clarify anything, let me know!
