The window balance springs are thinner than the standard balancer. they are 7/16 x 3/8. the channel is 21 inches long. the number stamped on it is S 208
Lauren from SWISCO responded:
July 19, 2023
Hello, thank you for posting,
Your balance resembles the S800-21 channel balance with a 20B stamp option. Please review and let us know if you have any additional questions!