I am unsure of which stamp (weight) option to choose.
The only thing I find on the old 27-inch balacer is "163 Japan", and on the old 19-inch balancer is "19 Japan".
I do not know the brand of the windows. The house was built in 1972 and the windows are the original windows.
Tom from SWISCO responded:
July 9, 2015
I'm not certain, either. Your best bet is to simply weigh your window sash and compare it to the chart we have on the S700-27 store page.