Need help with Anderson window part 139 5 23 1269

Hello,
I have an Anderson double hung window that the draw strings have broken I took the window apart and removed the balance boxes the numbers on the box don't match any numbers on your web site, my balance box numbers are 139 5 23 1269 the glass size per pane is 16" x 23-3/8" they are both the same size looking through the window the glass it self appears to be 1/4" thick so it's either a thick single pane or two thin insulated panes.
Thanks for any help,
Greg