channel balances

A stamp of 2630 usually indicates a 27" balance and a 2630 stamp option, so that's kind of weird. Re-measure the metal channel. It should measure 27" from one end of the metal to the other.

If not, the stamp is wrong and you need to figure out the option by hand, which involves weighing the sliding window sash. For that reason, if your channel measures any length besides 27", you should go ahead, remove the sash, weigh it, and get back to us with the weight and the true length of the balance.