Need Coiled Balance Spring

A handy person from San Francisco says:
Good morning. I ordered the S170-263 , but it was not the right fit for our windows. The attached photo are the two that we need.
Thumbnail of the uploaded file named Coiled Balance Spring - Hotel Carlton.jpg
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Bob from SWISCO responded:

Sorry to hear the S170-263 wasn't the right coil spring. Based on these stamps, it looks to me you need instead the S170-407 7 lb spring and S170-409 9 lb spring. However, please note that if these coils are on the same side of the window sash (i.e. one of them is stacked upon the other) then you in fact will need the S171-407 7 lb spring instead of the S170-407 . This spring then goes on top of the S170-409 . The video below explains more. 

A handy person from San Francisco says:
Thank you for the explanation. Can you please also give me the item number and description for the stacked housing for the coil spring?
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Bob from SWISCO responded:

Sure, see the 15-156 . We also sell the 15-157 drum, which you may also need.

SWISCO S170 and S171 Coil Balance Assembly
SWISCO S170 and S171 Coil Balance Assembly
VIDEO
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How to Replace a Triple Coil Balance System
How to Replace a Triple Coil Balance System
VIDEO
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