Replacement for my 28 3 HL CALDWELL balance

You're welcome in advance for the tips!

This is, as you said, a 29" non-tilt channel balance. It'll either be Series 380 or Series 385, due to the wings on the plastic attachments. Just measure the bottom attachment, the shoe, to tell which you need. The Series 380 uses a 1" shoe, and the Series 385 uses the 1-3/32" shoe in the picture. That would mean you need S380-29 or S385-29.

To determine the stamp option, you need to smush together the "28 3" code. You're going to end up with "2830" which is a common stamp option. You can check if that's truly the proper option by weighing your window sash. The 2830 option holds 16 to 23 pounds' worth of glass and frame.

With all that being said, you should be ready to order your balance!