which top sash guide for this channel balance?

A quick learner from Columbus, OH says:
Hi, there,
I bought this channel balances already (Series 351-25, option 2430). They work fine. But I need to replace several corresponding top sash guides. My existing ones have a weird shape which I can't find any on your website matching the exact shape.
I originally thought mine was broken 18-159P. But when I have 18-159P in hand, it appeared to be slightly different. They have different positions for the lower screw hole. So I start to wonder if previous people installed the wrong top guides.
Please help!
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Paul from SWISCO responded:

We believe you have the old Gapco top sash guide that has been replaced with our 18-157. The dimensions seem to match. Take a look and let us know what you think.

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