There were a number of ways to do this, all based on the idea that the head of the metatarsal (ball of the foot) should go on the center of the ski's contact length (the length of base in contact with the snow on a smooth surface).
Easiest way to approximate this is to put the ski on a flat surface and measure between the points where the edges rest on the surface. Divide in two to find the center of this line and mark it on the ski. The head of the metatarsal should sit at the widest part of the boot (the bulge on the big-toe side). On today's standard-sole boots, that's just about four inches behind the furthest-forward point of the boot toe flange, assuming a medium-size boot (250 to 275 approximately). If you want to get anal about it, use the average contact points. That is, press the ski flat on the table and mark the ends of the contact surfaces. Then let the ski return to full camber and mark the ends of the contact surface. Find halfway between the marks at shovel and tail, and measure that as the running surface.
There were simpler ways to estimate the location, based on half the chord length (straight line tip to tail) less 2.2 inches to locate the boot toe, but today's shorter skis have shorter tips and longer tails (relative to the contact points) so the old-school rules of thumb no longer apply.
In the case of your old VR17s (looks like 1977 or so), just assume that the toe unit is in the correct position and just adjust the heel -- you're bound to be within about a quarter inch. The skis will feel dead slow (ancient extruded P-tex) -- better tune and wax appropriately. Those Tyrolia bindings are probably from 1978. The engineering is good but I think you'll find they don't conform to the DIN adjustment scale -- they're probably marked 1-2-3-4 rather than 5-6-7-8-9. Most ski shops won't touch them. If you're going to ski them, replace that missing AFD, adjust the release in the middle of the scale and test the release function.
Dynamics from that era are fairly rare in the U.S., because the company was between national distributors. After Lange dropped Dynamic, they were imported for a few years by JP Jalifier in Aspen (his shop was L'Equipe), then by Frank Hurt in New Hampshire, until Volvo picked up the brand around 1979. The graphics changed dramatically then.
