A quick learner from Mesa says:
September 26, 2016
I would like to purchase two channel balance S380 34" 3320 19=005 15=005 how to determine the weight balance?
Tom from SWISCO responded:
September 27, 2016
Thanks for posting! You don't want the weight of the balance, you want the weight of the sash. You can determine this by taking it out of the window and placing it on a scale. Based on your stamp, the 3320 option should work for you. You can always weigh your sash to confirm, though.