Andersen balance 7#27

A home owner from Westtown, NY says:
Hi guys,
Really nice video showing how to replace the counterbalance on an Andersen double hung window. I wish I had watched the video before I took it apart, but it's such a nice video I'm gonna buy the replacement parts from you guys if you've got them.

What is the secret decoder ring you guys are using to figure out the replacement part?

I have about 8 different sized windows in the house I just bought that need new counterbalances.

Here's an example of one of them:
D78 7#27 3 87

I imagine the 3 87 is the date of manufacture based on the date of the house
What in the world is the D78?
Is the 11600-17 the part #?
Is the 7#27 the part #? Is that what you guys would call a 727 in your listings like this one: 24-737's just really confusing to try to get to the correct part and I'm gonna have to do 8 times over the next month or so.

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Paul from SWISCO responded:
Thanks for posting! I'm glad that our video was able to help you. Now, no decoder ring is necessary when identifying Andersen sash balances. The key stamp to look for here is the 7#27. As you suggested, the 24-737 is the balance you want to look at. It can replace balance boxes with the stamp 727.
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