Anderson window balancer
A handy person from North Stonington, CT says:
July 1, 2014
BD 16 7#27 12-86 is stamped on the bottom. I assume the 12-86 is manufacture date. 11600-17 and 11600-3 are also stamped on the balancer.
Donna from SWISCO responded:
July 2, 2014
Take a look at SWISCO product code 24-737, Andersen Perma-Shield Narroline double-hung window sash counter balance. This balance is used to replace balance boxes with stamp 7#27.