Very interesting history. The 1867 stamp is not mentioned in the Scott catalog, but may be mentioned in other catalogs -- perhaps Michel or Gibbons.
The information regarding the imperforate stamps being printer's waste must be why there are no catalog values for the imperforate Sc#1-4 stamps.
As for the 20c color error in blue, the Scott catalog shows values for both mint and used (with the used value being less than the mint value). Given this, there is a good possibility that there are more issues than just those that came from Hulot's effects. To be clear, I have absolutely no information to dispute what you offer, just a hunch.
Do you mind if I put your information in the newsletter? The next newsletter (April/May/June) is already filled, so it would not appear until the July/Aug/Sep issue - if you agree. Do you know where the information came from?
Thanks for sharing. I love new information. Regards, Tim
Tim May your collections grow beyond your album capacity!