Inherited A Stamp Collection With A Rare Stamp?

Can someone help me identify these stamps for me? I inherited a stamp collection recently and this stamp stood out of course so can someone help me identify it? I think its 424B or 424F. In the stamp catlogue it says to refer stamp 424B as 423D. This stamp is on a postcard and I saw the value. Am I reading this correctly. Its labeled and everything.

Well, it's certainly not a pair of stamps, so I don't see how you can claim that it's imperforate between. I don't have my catalog in front of me right now, but I think it is a pretty common stamp.

(Maybe the errors were inside the envelope?)

Oh actually there are more stamps in the envelope, I separated them so they didn't touch eachother. I'll upload the pics right now.

look for a pair of stamps with no perforation holes between them.

If you are referring to the first scan, that is not an "Imperf between" it is called a natural straight edge. This happened when the sheets were cut into 4 panes. In order for a Stamp to be verified as an imperf between it must be an attached pair, not a single stamp.

As I read the notes, the original writer was claiming that the straight edge examples were cut apart from 424f pairs. But the catalog is pretty clear that 424f is for a vert pair imperf between with a straight edge at the top. None of the four target stamps has a straight edge top and bottom as one severed from such a pair would, let alone the question of a pair.

However,

The first note refers to a 424b, which Scott has elevated to a major number as 423D, based on compound perfs 10x12 and watermarked 190 (single line wmk). In current Scott, one on postcard cats at $22500. So one of those without the straight edge is supposedly compound perfed? I don't think so.

Does anyone know what stamps these are if you think they aren't 423B or 424F?

I would guess just 424, with the side straight-edge samples possibly from the booklet version, 424d. (A perf check would help us out.)