strength of spring in vinal window channel balance

Thanks for posting. I'm afraid I don't know what that stamp means. I see you were looking at our S775-26. Is this the Series and size you need? If so, I recommend weighing your sash on a scale and referring to the chart we show on that store page. That will tell you what option you need beyond any doubt.

I do not advise guessing or estimating the sash weight. It's important to be as precise as possible.