The experiment with my grandfather's skis was a success. I really don't know how old the skis are. They have no name or trademark that is visible to me. The bindings are Thorleif Haug brand. Haug was a 3-gold-medal winner in the first (1924) winter Olympics so the bindings are from that time period.
Suffice it to say the skis are close to 100 years old. They certainly meet the specs of skis from that period. Those were referred to as Telemark skis and represented the best all round type of ski. Good for cross-country, downhill, and jumping. A typical one had these dimensions:

The main difference between my grandfather's ski and this one is the absence of a mortice where the binding toe plate would have been located. His bindings are screwed onto the ski. That probably makes the ski about as old as the binding, i.e. from the 20s.
All of the stars lined up to make my experience with these skis so enjoyable. I found a new area to explore. I had it all to myself, i.e. first tracks. The snow conditions made for extremely easy solo trail breaking: 3" of fresh dry powder on top of a rain crust that supported my weight without problems 99% of the time. The terrain was gently rolling. I had a wide open field to practice in.
The bindings had to be modified for my use. The old leather straps they had were too fragile and lacked enough scope for my boots. I substituted some Rottefella Chili heel wires. I expect the leather straps, when new, would have provided a similar feel.
The summary of the skis is that they worked great in these conditions. They track well with a deep center groove and substantial length (>210 cm, but not 240 like the diagram.) The open field provided ample room for wide turns. Tight turns, especially on thin powder over icy crust and no metal edges were more difficult. I think in deeper powder the skis would perform even more admirably but still be hard to use for short radius turning. They are not light. I believe they are made of hickory which is a pretty dense wood. I have a picture of my grandfather cross jumping on these skis. I can' only imagine how difficult that must be.
There deep powder performance awaits to be tested but with today's fascination with "early rise" and "rockered" skis for powder it's not hard to believe these would perform well since that was the ideal for the shape of the front of the ski in those days. From Caufeild's
How to Ski, comes this admonition: "The turn up at the front of the ski should begin at about one-fifth of the distance from the tip to the heel end.
It should be very gradual,
for a sudden bend makes the ski run more slowly and far less smoothly. The under side of the tip need not be more than five inches above the ground."
Hopefully I'll get a chance to find out sometime later this winter. If not, I'll go back to the same spot and find out how they like spring corn snow.