need help identifying a window balance

Thanks for your photos. Based on what I see here, you have either our Series 380 or Series 385, 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.

Comparison of the S378, S380 and S385 balance shoes.

Your stamp of 26-5 usually corresponds to our 2650 option for a 27" long balance, but getting your sash weight will verify that. To get your sash weight, all you have to do is remove it from your window and place it on a scale. Any common bathroom scale will do.