Searching for 54 x 77 window sash H LC50

Thanks for reaching out. Your balances appear to be either our S380-37 or S385-37 Channel balances. To confirm the correct replacement you'll need to measure the depth of the bottom shoe on your balance. You may use the diagram below for reference, If your shoe's measurements differ for what's shown, let me know.

Comparison of the S380 and S385 balance shoes.

Please also note, I am unable to cross-reference the stamp you have pictured. You'll need to get the exact weight of the sash so that you can confirm the weight range the balance will need to be able to hold.

Once you've confirm which series you need, you'll be able to confirm the stamp using the chart below the product description.

The bottom shoe in your photo appears to be damaged so that could be why you're seeing a measurement of 3/4". We don't sell a 3/4" shoe and are unaware of that size ever being made.

Would it be possible for your to remove an undamaged balance from the window so that you can get a more accurate measurement?