Searching for I have the 17" series 350 channel balance with a stamp of: 16BUSB. which weight option is this?

I'm sorry to say that I don't know what that stamp represents. That's a pretty odd one. Would it be possible to see a photo of it? Sometimes seeing how the numbers are printed is as important as the numbers themselves.

If all else fail, knowing the precise weight of the sash will let us cut right to it and determine what option is best for the window.