Hello Sylvain
The following to your questions,
This is the brand catalog number 31 according to Zumstein or SBK.
Image 2: The double line, double edge lines are due to the so-called spikes of the blocking material, pieces of lead, cards or paper strips used to level the printing blocks.
The following about the color:
There are blue, dark blue, greenish blue, vivid blue and light blue. These shades of color are cataloged.
Sorry about my English, google had to help.