Window channel lock with numbers to 2420

Hi there- thanks for posting! 

We'll need to see the entire balance removed from the window to be able to determine the best replacement option for you. The stamp that you've provided a photo of only tells us the strength of the balance according to the weight of your sash. Unfortunately, it doesn't tell us the Series of the balance which is the most important aspect. Send us some photos of the end attachments on your balance and we can get the ball rolling on finding you a replacement! 

Yes, thank you! This is a Series 351 or Series 390 balance, depending upon the depth of the bottom attachment, as shown below. The 1-1/8" shoe would indicate you need S390-25 and the 1" shoe would indicate you need S351-25.

Comparison of 15-001 & 15-002

No, that's the wrong measurement. Measure front to back as shown in the photo. The 1-1/8" dimension is the one you want to look at. You probably will struggle to obtain this measurement with the part in the window. I wouldn't recommend attempting it that way. Consider removing the part.

I really can't tell from a photo. Perspective makes a huge difference, like when people take photos of themselves holding up the leaning tower of Pisa. Only you can measure the part accurately since you have it in hand.

You seem to be trying to identify the balance without removing it from the window, which is a very unreliable method. Take a look at this video and see if it helps you get the balance out to take the right measurement: