The balance I took the picture of is a old one and says 2740 not sure what window this one came from. I used your method of calculation for the weight and have 2 windows that are 24.87lbs., and 6 windows that are 28.79lbs., and all use this same style balance that measures 28 inches long. Please tell me what you reccomend for these windows as the original balances were all different and the windows never worked very well.
