We think this is a WindowMaster 610 series Non Tilt Channel Balance purchased at Home Depot purchased around 2000 or 2001.
The Problem is the Nylon Roller seems to have been frozen stuck and worn on one side as you can see in the photo where I'm lifting back the hook, this is causing the window to Freeze and Finally the Channel Balance itself just fell out.
The Guide-Rail (only the metal rail) is 21"
The Bottom Shoe is closer to your 15-004 (confirm with attached photos)
The Stamped Marking on the rail appears to say:
2020 B.S.I, ND (confirm with attached photos)
Please let us know if you can determine a good replacement match from the photos and supplied information.
Thanks in Advance,
Daniel
