non-tilt channel balance stamped 3190 BSI 35

A contractor from Walnut Creek says:
Need to replace a pair of these channel balances, seem to correspond to your 380 series, although nothing you offer matches the 3190 stamp. Can you identify/supply replacements?
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Bob from SWISCO responded:

Thanks for writing in. This certainly looks potentially like the S380-32; the only other possibility is the S385-32. The only difference between these two balances is the 'depth' of the bottom nylon fitting, so compare both with your old hardware to see what matches best. The 'depth' is the distance between the heel-and-toe of the shoe, just below and perpendicular to the metal channel. As far as your stamp code, 3190 is from an older ratings ystem we no longer use. To know what stamp option you should select, weigh your window sash. You can then match that exact weight with one of the weight ranges alongside each stamp option on the product page.

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