Correct balance for 40 Pound window

Hello,
I've looked through your very helpful web pages and settled on the balance I need.
The channel width is 1/2 inch, the top is a 19-005 and the shoe is a 15-004. The length is 34 inches which gets me to the series S385-34.

The problem is that the stamp code on my old balance doesn't match any of the series options. The old balance code is 33 9 LR CALDWELL. The weight of the window sash is 40 pounds. The available options are as follows:

Stamp Option Sash Weight Range
3310 8 to 13 lb
3320 13 to 18 lb
3330 18 to 23 lb
3340 23 to 28 lb
3350 28 to 32 lb

It doesn't appear that any of the available options match the weight of my window sash.

Can you help clarify?

Thanks!