Replacement window balances

A handy person from Eaton Rapids, MI says:
My name is Joe and I'm searching for replacement balances for a friend. They have late '70's double hung, tilt-in, wood windows with thermopane glass. Don't know mfg. of windows but the balances I found with you folks look exactly like the ones I'm replacing. The series 751 look and measure correctly but the old balances are only stamped with 24 for one size and 36 for the others. I'm not finding any other numbers stamped on the balances so don't know any option that may pertain. The one's stamped 24 actually measure 25" however, end to end as shown in your documents. The shoes measure exactly too, to what is there. Any help would be appreciated. I'm looking for 6 ea of the 24's and 6 ea. of the 36's.
Thank you,
Joe D.
Profile picture of Donna
Donna from SWISCO responded:
Hi Joe,
For the Series 751, Ribbed Channel Tilt Balance, the stamp for the 25" will normally start with 24 and the stamp 36 will normally measure 37", please measure the 36 to check.
Please remove the sash for the 25" balances and remove the sash for the possibly 37" balances and place each on a scale. We need the weight of the sash in pounds to determine the proper stamp option.
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