Good blog post and thanks for writing it. But though Babbage's work may not have been lost for quite as close as 100 years, there is truth to the usual history and I don't think these two examples establish the "turns out to not be true at all":

• Charles Babbage lived 1791–1871, dying a couple of months before his 80th birthday. He wrote his Passages from the Life of a Philosopher in 1864.

• The Swedish difference engine, produced by Scheutz father and son, is mentioned in these memoirs. At the time, it was regarded as a smaller-scale/toy/prototype version of the Difference Engine he was engaged in building. So, even though this version did find use "in production" (at the Dudley Observatory at Albany, and an English-made copy in use "the department of the Registrar-General, at Somerset House"), it was still short of what he actually wanted to build (or had promised to build).

• As for the example you illustrate of W. Stanley Jevons's praise in 1969 of the Difference and Analytical Engine, this too came during Babbage's lifetime, and was for the idea rather than any concrete details of the design: "in his subsequent design for an Analytical Engine, Mr. Babbage has shown that material machinery is capable, in theory at least…" etc.

So it does seem to be the case that at least after Babbage's death in 1871 (if not before), his ideas for the Analytical Engine were dismissed as impractical, or absurdly expensive, or a failure, etc, and no one quite looked at them at least until (going by the Aiken reference you found) 1936, which is 65 years.

Wow this really brings home how recent it was still in the scheme of things. I had it in my mind before this thread and article that Babbage was in the 1600’s or something.

But did Von Neumann also lead us towards a security nightmare? Code is data is very powerful but also a Pandora's box from a security perspective.