Balancer 2501 B.S.I.

Thanks for your photos. Based on what I see here, you have either our S380-26, S385-26, or S378-26 depending on the depth of the bottom shoe. That's the only difference between them. I recommend measuring your shoe and referring to our dimensions to confirm the best match. 

You will need the weight of the sash to determine which SWISCO stamp option is best for this application. Your existing stamp is honestly a little peculiar, so if you don't see your sash weight represented on the chart for any of the above balance's store page, just let me know.