Bob from SWISCO responded:
December 10, 2023
Thanks for posting. It appears both fittings lack side tabs, or what we call wings. Is that accurate? If so, this is either an S351-27 or S390-27. The only difference between these two channel balances is the depth of the bottom nylon shoe, or the 'heel-to-toe' measurement. See the illustration below for reference. Compare both balances with your old hardware to see what matches best. For a stamp option choose 2630. Comparison of the S351 and S390 balance shoes.
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