These materials are from that remarkable past; they capture the spirit of that era, which is in many ways different from today's, and it must be said that the sound of that time was more natural and memorable. Therefore, those recordings are very valuable, but they often lack quality, which is not surprising given the technical equipment of the time. High-quality restorations and upscaling can remedy this, but the neural networks are still too weak for excellent results.
That's a good idea.

Pierre, do you have a lot of other materials from the past that remain hidden in a stash, hidden from the connoisseur viewer?

Yes of course ... A LOT !!!

PW