Channel balances with "28 3 JR CALDWELL" inscription

I measured the width of the bottom plastic piece at 1 3/32 inch. I measured the entire length of the metal channel at 29 inches (despite the inscription calling it a 28). I tried to include more pictures but was limited to five. It's a half inch wide channel. I identified it as S385-29 for a non-tilting window sash that weighs 16 pounds 2 ounces, but before I order 10 channel balances I want to be sure I'm ordering the correct model.