Gerkin Window balance
Thanks for posting. These appear to be an older style crossbow balance which has been discontinued and is no longer made. There is a chance you may be able to use our Series 795 as a replacement but there are a few pieces of information you'll need to confirm before we can determine that.
To start, review the video below for the details you'll need to confirm to confirm if this is the balance you'll need.
In addition to this information, you'll also want to confirm that the width (diameter) of your spring is 1/2". If the spring is not 1/2" in diameter then the S795 retrofit will NOT work, but we can find alternate solutions,
Please be aware, to confirm that all of the measurements, you will need to remove the balance(s) from the window.