Like lots of good stuff, it all started in a garage.
Better than leather: heavy-duty synthetic felt and nylon webbing combine in the Double Accessory Strap Holder.
#00 spur grommets, made for us in the UK. Yes, we took every detail quite seriously.
The internal frame . . .
. . . is removable.
Two pie-slice cut-outs on each edge allow the frame sheet to flex in use.
The 6061 Aluminum stay is removable. Soft plastic caps insure the rest of the pack can't be damaged by the stay.
We pre-bend the stay to a gentle S-curve to approximate the average spinal curve.
Carefully bending the frame sheet and stay over your knee (or knees for a gentler curve), you can adjust the curve if you so desire (though you needn't remove the frame from the pack).
The back and bottom of the Guide's Pack are fully padded with .25" / 6mm closed-cell foam.
Six flat pockets on the interior back panel accept the six "fins" of the frame sheet . . .
. . . firmly holding it in place against your back.
Curved, thermo-formed, die-cut, padded shoulder straps: we just didn't have the technology to make these 40 years ago.
And who woulda thunk it: pockets for a cell phone and a GPS.
But then again, the best things in life really haven't changed.