Resersing tells me this.
There are no metal stampings on the "plain" channel tube.
Stamped on in blue is: AGU 29-5 GB5 CMC 25
I measure the length of metal tube to be 29-3/4"
I believe the "hook" "top" piece is nylon with dim between th foot and the hook 1-1/6"
The other end is called "winged" also nylon.
The weight of the sash is 35.4 lbs.
Your 2860 or 2865 are probably the correct sizing..
Robert