There are 2 editions of this block. In the first edition all stamps are printed with 80 dots per cm. The 2nd edition the 12+8c is printed with 100 dots per cm.
The 'loose' stamps, from sheets (NVPH 870-874) are all printed with 100 dots per cm.
A loose stamp 12+8c (NVPH 871) from a block can be distinguished from a sheet stamp by the printing direction. With the bubbles, the printing direction is downwards (the printing ink runs slightly downwards). With the blocks, the printing direction is upwards and the printing ink runs out slightly at the top.
This block (NVPH 875a) was printed wit 80 dots per cm.
