I believe we can supply this balance, but before I recommend anything I'd like to see a clear photo of the top plastic fitting. Your pictures here only show the bottom, but I need to see both before I can narrow down the list of possibilities. Thanks!
What you're showing me here is still just the bottom fitting. To clarify, we need to see the plastic fitting on the opposite end of the balance.
Thanks for your photos. Based on what I see here, and your stamp of "21C," you have either our S351-22 or S390-22, depending on the depth of the bottom shoe. That's the only difference between them; both are 22" long and otherwise have the same configuration. I recommend measuring your shoe and referring to our dimensions to confirm the best match.
A stamp of "21C" usually matches our 2130 stamp option, but I would suggest weighing your sash on a scale to confirm. Two 22" long balances with a 2130 stamp can carry 12 through 15 pounds.