Which window sash channel balance should I order?

A home owner from SF Bay Area, California says:
July 14, 2011
I need a pair of replacement window channel balances--this will probably be a custom order

Here is the basic info:

Length: 28"
Width: 1/2"
Label: 27 4 HP Caldwell
Window type: Non-tilt
Only the bottom sash opens

Attached are pictures of its top and shoe; the shoe has wings.
User submitted phots of channel balance top and bottom attachments.
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Paul from SWISCO responded:
July 15, 2011
Thank you for posting.

The photos were taken a bit close (particularly for the top guide), but it seems very close to the Series 390 Channel Balance.

The "27 4" stamp translates to 2740.
A home owner from SF Bay Area, California says:
July 15, 2011
Thanks for your response Paul. Attached are additional photos. The Series 390 does not appear to have wings on the shoe, where as the ones I am seeking to replace do. Does that matter?
User submitted photo for bottom attachment.
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Paul from SWISCO responded:
July 18, 2011
Does the top shoe have wings?
A home owner from SF Bay Area, California says:
July 18, 2011
The top shoe does NOT have wings. Thanks.
Profile picture of Paul
Paul from SWISCO responded:
July 19, 2011
Although we do not offer this set as as a specific series online, we can create the balances for you.

To begin, please fill out this Custom Balance Order Form. After you submit the form a representative will contact you regarding the ordering process.

Please let us know if you have any questions.
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