Mi 8 Type 1 Half Imperf Oddity
This has the top and left side perforation 10, and the other two sides are imperf. Very strange. The stamp is genuine.
I thought the perforations look rather standard for this issue, and the imperf edges are consistent with a Mi 7 imperf and a Mi 10 imperf that I have.
However, the consensus of some people at ChicagoPex 2014 is that it's very unlikely the imperf edges are genuine:
Note the low dot between the 1 & 8 in 1918. If that is a consistent mark, perhaps this issue can be plated.
Read a PDF with my detailed analysis.
See other oddities: Cat #'s 2, 3, 4, 5, 6, 7, 8, 15, 16, 18.