Identify this part please

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.