Thanks for your reply.
Regarding the sash weight, my scale says 33 lbs. Not knowing the scales true accuracy, it looks like I am on the boarder of an option 3440 and 3450.
What do you think? By the way, the sash is 17 years old, but the reason the balance failed is because the rivit pin used to hold the spring failed (pulled through the channel holes). Make sense?
Go with option 3450?
If the original balance was 3440 and lasted 17 years, I would stick with that. 17 years is a long time for a balance!