Congratulations on your find. Mine are an earlier mode from 1985 set up for Bruce Gordon racks front or rear. They have three hooks along the top rather than two on yours and two hooks parallel to where the horizontal strap is located on yours. I have no horizontal lower strap. I use the high front Mountain Bruce Gordon rack not the low rider version.

The panniers reflect Bob Beckman's lengthy touring experience. I marvel at the little things he built into these bags. Wonderful on and off pavement.