Caldwell balance identification

A quick learner says:
Hi, I'm trying to locate replacements for these Caldwell window balances marked: 27 5 HQ Caldwell

I have attached some photos below. Could you tell me what part number I need to replace these?

A customer submitted image of their channel balance hardware.
Profile picture of Tom
Tom from SWISCO responded:
Thanks for posting, Matt. Before we can determine what Series you have, we'll first have to decide what bottom shoe that is. Take a look at our 15-001 and 15-002 and let me know which one is a closer match.
Alternate view of 15-001
If it's the 15-001, then you might be looking at our Series 390 channel balance. If it's the 15-002, then you should consider our Series 351 instead.
A handy person from Long Beach CA says:
I have the 15-001 so I'm looking at the Series 390. I'm a bit confused about the length though, it measures 28" but it is stamped 27 5 HQ. How do I determine the sash weight range?
Profile picture of Tom
Tom from SWISCO responded:
The length sounds accurate. Usually the first two digits of the stamp is one number less than the length. A 28" balance with a stamp of 27 5 is normal. As for weight, you will have to remove the sash from the window and place it on a scale.
Reply to Thread
Use this form to ask a follow-up question or to share your experience regarding this subject.
(your email address will be kept private and is only used to inform you when a response has been made)