Replacement part

Thanks for posting! It sounds like you need a new replacement balance. However, I cannot identify it based on just the stamp. All that tells me is how strong the spring is, not what the Series is.

That said, it appears you have a Seasonall brand top sash guide in your third picture, like our 18-110. This leads me to believe it's a Seasonall brand window, which has been known to use our Series 390 channel balance. I recommend carefully looking over the pictures and information we have for this hardware to confirm that the Series 390 is a match. Make sure to take special note of the nylon attachments on either end.

It also looks like your window lock in the second picture is broken. See our 90-402 for a possible match, if you need it.