Non- tilt wimdow

Thanks for posting. It appears there are not 'wings', or side tabs, on either the top or bottom nylon attachment. Is that correct? It's a bit tough to tell. If so, this is either an S351-23 or S390-23. The only difference between these two channel balances is the 'depth' of the bottom nylon shoe. See below. Measure your old balance's shoe depth to see what matches best. For a stamp option choose 2240.

Comparison of the S351 and S390 balance shoes.