Lawson window replacement parts
This looks like either an S380-30 or S385-30 Channel Balance. The chief difference between these two balances is the depth of the bottom nylon shoe, or the 'heel-to-toe' measurement, so compare both with your old hardware to see what matches best. Your stamp of 29DS42 is from a rating system we do not use. The second pair of numbers should indicate the window weighs 42 pounds. That means you should be able to use a stamp of 2970, which can support a window sash in the weight range of 39 through 42 pounds. You can weigh your sash to be safe to confirm if fits this range. Let me know if you have further questions.
All orders can be placed right through the online shop page. From the S385-30 shop page, simply click "Add to Cart," and then click "Checkout" at the top right hand corner of the screen. Don't forget to set the quantity and stamp option needed.