351 balance

Thanks for posting! I'm not sure what your question is. If you were wondering about the stamp, the answer is that some older manufacturers used "90" as a mark for sash weight. However this rating system has fallen out of use for more modern systems. One of the standard stamp options for our S351-22 may very well work for you, but you'll have to weigh your sash and refer to the chart we show on that store page to confirm the best match.