WeatherShield 2420 then a marking that looks like a capital F missing it's leg

Question

These windows were purchased in 1986. We need several balances.

Bob · Accepted Answer

Thanks for writing in. It looks like the bottom attachment has 'wings', or those side tabs, while the top fitting lacks them. If so, I think this is an S350-25 Channel Balance. Please compare. For a stamp option choose 2420.