I just posted the photos to show what might happen, and because it is an oddity. IMO someone didn't take good enough care of his equipment as he should have.
I'm not upset in the least. I got 2 pair of barely used, top-of-the-line Volkl skis for $20.
The pair that had these bindings on them were in great shape, still some of the original base structure visible and lots of the factory grind on the edges left. And, as a matter of fact, my favorite ski model. The other pair were basically brand new, maybe had been skied on 5 days.
And, OK, its a M51. Funny, another pair of M51's I have actually have a "1" on them.
And what you say about springs makes sense, at least from my very limited experience and what I remember from Engineering Mechanics. The few pair of bindings I have seen over the years that had bad springs were the result of a much too large skier using them.
Oh trust me, I get it. It has nothing to do with a person not taking care of his gear, the bindings are old, plain and simple. I am not sure why so many skiers think this stuff should have an infinite life span, I see it everyday here at the shop. Some guy has been away from the sport for 20 years, brings in an old pair of skis and wants me to work on the bindings. I inform him that I cannot (or will not) and why, and I get accused of trying to pull some scam to get him to buy new gear. I really don't give a shit if a person chooses to use 10, 20, 30 year old bindings, but I certainly will not involve myself or my shop in that situation.