29-15 channell balance

That stamp is kind of funny. Can we see a photo of the balance? Ultimately, the stamp identifies the spring and a different, unrelated product code identifies the balance assembly. "29-15" is especially odd.

To sort this out, send photos of both end attachments on the balance. We will also need the length of the metal channel, and the weight of the window sash. It's a lot of information, but we need to be careful, since custom balances do exist, and this may be one of them.

That's a common balance, and "29-xx" type codes usually correspond to 30" balances. Sounds like that's your best bet, though it never hurts to measure closely.

Just be sure to carefully compare the weight of the sash to choose a stamp option. "2920" may be ideal, but I'm not sure. "2910" seems too weak.

Let us know if you need anything else, though! Thanks for coming to SWISCO.