3401 stamp for a Series 770?

A home owner from Newport News, VA says:

August 6, 2016

Hi,
I need to replace a broken balance. As far as I can tell (identified based on pictures on your site) it is a S770 34" long. Only trouble I have is to find out what option I need (A-D?). The old broken one has a stamp "3401 BSI BL" while the opposite one (still working) says 3401 NC BSI.
Please help. Thanks.
Bernd

Paul from SWISCO responded:

August 9, 2016

Thanks for posting! That stamp uses an older weight rating system that the manufacturer has phased out. One of our standard options may still work, but you would need to weigh your sash on a scale to confirm. We have a chart on the S770-34 store page that shows how much weight each option can support.

34" Series 770 Balance

S770-34

$13.77

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