Most of your stamps are to some extent sub-standard... either in colors or cancellations etc so the possibility arises that they were test overprinted on lesser quality stamps.
Yes, I noticed the same thing, at least about the cancelled stamps. They were altogether with some others that, while they do not have overprints, are also somehow flawed. I wish I had the full story.
Maybe I'll add them to my growing collection of forged Barquitos. And yes, maybe I will also write this bunch up for publication someplace eventually.
Did anybody notice that several of them looked as if the overprint itself was almost 3-dimensional? I used a very good macro lens to make the images, and I wonder now about the way the overprint almost seems to be sitting atop the stamp. It's very noticeable (at least to me) on the first two 1/2 penny Office of Works stamps that I uploaded last night.
Would that be a signal of a forgery?