S390, with a groove

A quick learner from USA says:
No wings on top or bottom, and the shoe is more than 1" deep.
Please confirm that this sash balance is s390 - 27.
Note the groove on the top piece.
User submitted photos of a window balance.
Profile picture of Paul
Paul from SWISCO responded:
I'm afraid I cannot confirm if the S390-27 can work for you. Your pictures only show the top attachment. While the top attachment certainly appears close to the 19-002 that comes with our balance, I cannot speak for the bottom attachment. The groove you mention in the top attachment does not matter, so you don't have to worry about that. However, we have detailed information, pictures, and measurements on our site that you can use to confirm whether the S390-27 is a match.
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