What stamp option does my Series 380 channel balance need?

A handy person from San Diego, CA says:
January 13, 2012
I need a couple of replacement balances and have been able to identify the closest replacement in the S380-28. Unfortunately, the associated "option" criteria for the balance doesn't match the existing balance. The existing balance only has the following markings on it: "27 3 HU CMC 2" and no stamps in the metal itself (see image1).

Also, the top piece "19-005" and bottom piece "15-005" are the closest to what I have with only minor differences (mainly on the top of the top piece) - not sure that this will be a problem (see image2)?

Any help is greatly appreciated, would like to order replacements... Thanks!
A customer submitted photo of channel balance attachments.
Profile picture of Donna
Donna from SWISCO responded:
January 15, 2012
Hello,
Normally a 28" Series 380 balance with stamp 27 3 will translate to 2730.
To check, remove the window sash and place it on a scale.
S380-28 with stamp option 2730 will carry a window sash weight range of 13 through and including 19 pounds.

This information is based on 2 balances per sash. Balances are designed assuming friction in the jamb weather-strip will carry a portion of the sash weight. Suggested sash weights are approximate.
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