Channel balance

These stamps typically indicate the calibration of the spring, though your stamp in particular isn't one I'm familiar with. That might indicate a custom calibration, but I'm not sure about that.

Before we go any further, I see that you were looking at our S385-29. Is that the balance you have? If so, you can weigh your sash on a scale and refer to the chart we show on the S385-29 store page. That will tell you for sure if any of our standard stamp options can work as a substitute.