I would appreciate your opinion prior to order these, will need 30 units. The metal is 27" long and the bottom shoe is 1" so it appears that the
S351 with 2640 is the correct replacement. The stamp on the metal is 2640 with a special character after the number. The 18-09 appears to be the best fit on the top sash guide, the top is not as square as the existing and the screw holes are circular instead of elongated but the measurements are similar.
Appreciate your assistance