H17 623 6-8 Andersen sash balance

Hi,
I hope you can help me without having to go back to the jobsite. I'm working on a double hung Andersen built "about" 1987. The balance has several numbers on it: H17 623 6-8, 11600A-3. Without a magnifying glass the ID on the pane had C1G-2 4-00. However the last two digits may have been "88" or "86". The sashes themselves are 28"w x 23-1/2"h. (Yeah I found out now that Andersen wants visible glass size). Maybe I've given you enough info to find the right balance. One 'box' has two balances in it. My friend at the lumberyard thought it had one on top and one on the bottom, but not this one. It also has two screws on the lower left side (from the inside) sash liner for removal. Thanks Gary D