Marvin Tilt Pak Springs
thanks for your help!
Hello,
The knife lock shoe shown in your photo resembles part of the Series 751 channel balance, which uses the 15-014 shown below. Review the specifications of the shoe and confirm that the top of the balance uses a rivet for installation as shown below.
As for your stamps, they do not match the strength options shown on the S751-21 and S751-27 product pages. Our balances can still work but you'll need to weigh the sashes that the balances support. There are charts under the S751 product descriptions that show the weight ranges that each option supports. Take a look and let us know if you have any other questions. Thank you!