Non-tilt block and tackle channel balance

name of manufacturer : unknown; stamped on part 28E; length is 29" (inches); length of wing is 1"; height of of 15-005 shoe os 1"; top and shoe has 1" length wings; channel balance looks like S380;
Don't know if it is a 2840 or 2850 channel balance. It's for a non-tilt single hung window. The insulated window panel that it controls is 46" wide and 30" high.

Thank you. Will order shortly.