this appears to be a Series 395 with 19-005 top and a 15-001 bottom. the aluminum tube measures 30". However, there is stamping on the channel that notes 29-5 and smaller letters PA D31. By chance does the 29-5 indicate 29" length despite the 30 inch measurement?
the window sash weight 13.9 lbs so that makes it option 2920 Correct
Thanks for checking in. The 29-5 stamp typically corresponds with the sash weight range and is one digit lower than the length. So, it sounds like you're on the right track with an S395-30. However, if your sash only weighs 13.9 lbs., you would be correct to use the 2920 option instead. Let me know if you need any further clarification.
You always want to stick with the exact weight of the sash. Going with a stronger weight option will cause the window to not be able to close since the springs will be too strong. If you feel the stamping on your current balances may be wrong, then you can always weigh your sash on a scale to get the accurate weight and chopose a stamp option based off of the number.
