37 inches
Thanks for reaching out to us! We'd be happy to help with this. We'll just need more information. Can you show us some photos of the bottom fitting along with the metal clip attached at the end of the cord?
Thank you! The bottom fitting is the part in your first photo here. My recommendation is either the S380-37 or S385-37 depending on the depth of the bottom fitting. You'll have to measure as shown below to determine the best match.
Your stamp doesn't match any of our strength options, however. Can you weigh the window sash on a scale and tell us what you find?
In that case, see the 3630 stamp option. A pair of balances with this stamp will support a sash weighing 18 to 23 pounds.
The difference between the Series 380 and Series 385 is the depth of the bottom shoe. See the image below. You'll have to measure your old shoe to determine which Series is best for your window.