anderson window sash balance replacement part

I need two replacement sash balances it says Anderson Corp, Bayport Minn and then 11600-17 on the flat body. There are faint numbers and spaces on the tab (with a staple) at one end but they differ between the two identical units I pulled out of identical windows. perhaps these are lot numbers? I think they're irrelevant but here they are anyway:
1131 1 6 9 92
927 1 0 1292