Excellent information Al. I do believe your information is correct from what I read in the past. Thank you for sharing it in the forum.
Below are other photographs I would like to share with the room pertaining to 3 mm and 2mm differences.
This is a block of 6 Washington 332's that are also 3mms as well. I always look at the perforations carefully between stamps with the Scott's 332's. If you line them up on a 2mm, they are not the same width size. The perforations are not directly in the middle between stamps. In the block of 6, in the top margin is also have the pin holes.
The Benjamin Franklin block of 4 also came along with the collection of unused stamps.