How do I determine the window sash weight

A home owner from USA says:
I have the part number 34C BS1 which translates to Series 765 Balance, product code S765. I need a 35 inch replacement so S765-35. The balance in the window does not have a sash weight stamp. The window is large, 35 Inches by 32 1/2 for the bottom pane. How do I know what weight option I need. Do I have to weigh the window???? They are double pane, single hung new construction windows from 2004. I am guessing Anderson brand, but not sure. Would like to get this done ASAP as home is being sold the end of the month. second question: how long will it take to get the part? Thanks for the help.
Profile picture of Tom
Tom from SWISCO responded:
Yes, if your balances do not have any stamps then the only way to determine what stamp option you need is to place the sash on a scale and compare it to the chart we show on the S765-35 store page.

As for how long it will take, we offer several shipping methods to choose from, so it will depend on what you choose.
Reply to Thread
Use this form to ask a follow-up question or to share your experience regarding this subject.
(your email address will be kept private and is only used to inform you when a response has been made)