Thanks for the reply Jack ,I just thought the thin rubber blades would distort when the mower was cutting grass but obviously they were made to bend if anything came into contact with the spinning rubber blades .
It sounds like the original blades would be lucky to last 10 years as some manufacturers of garden hose at the time only guarantied rubber hose to last 10 years.
The great disappearing mystery of rubber fan blades makes sense now ,this reminds me of the weird phenomenon of disappearing garden hoses from the fifties where Garden hoses started to spontaneously burrow their way into the dirt and would never be seen again ,many were cut loose at the tap.
