1851-57 12c Washington

Here is something that I ran across (do not own).
Both stamps have a PSE cert saying it is genuine Scott #17.
Both have a weak outer frame line and lower right guide dot
is right of the inner frame line. That makes these stamps plate 3.
Siegel calls these stamps Scott #36Bp5 on stamp paper.
I think they should be called Scott #17B.
Apparently, half a sheet was made imperf when the sheet was created.
Not sure if that means half a pane or half of the 200 stamp sheet.
Both of these stamps are left pane unidentified plate positions.
Only half of the left pane has been plated.
They are two of the 44 missing positions.