1400s amateur crypto and human puzzle tendencies

[Mark Knowles]

@Mark, I wouldn't be surprised if you've stumbled across the right key or application a few times, but didn't notice it.

I have certainly seen a lot of early 15th century ciphers and not studied many of them in nearly as much detail as I would have liked. However there are also big gaps in the cipher history, that I know of, from this period. I would love to see a Milanese cipher key from between the years 1425 and 1444.