Andersen Balance No Tab?

A home owner from New York says:
Based on the numbers on my sash balancers I am needing to replace, I was looking to order your part #1226. However upon closer inspection I see a difference in the balancer where the pictures of your balancer shows it has a tab for the fasteners and the one I have does not.
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Bob from SWISCO responded:

A stamp code of 1226 indicates you'd need our 24-1231, which can replace old Andersen balances that have the 1226 stamp code. You are correct, however; that tab on our newer balance boxes is an important difference. What you'll need to do is chisel out space in the window frame to make room for the tab. This blog post here goes into more detail, and also has a video detailing the removal and replacement of these Andersen balances.

How to replace an Andersen Window Balance
How to replace an Andersen Window Balance
VIDEO
WATCH >
Andersen's Narroline Sash Balances
Andersen's Narroline Sash Balances
GUIDE
READ >
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