Also known as ACSC 136c, this is a booklet pane of 4. Not in the best shape, but bought at a bargain and fills a nice hole. If you did not have a pane of four, the best way to tell if this is a booklet stamp is the presence of a dot in the center of the top and bottom margin of each stamp (which is sometimes removed by the perforation). This can easily be seen in the left two stamps, but not in the right two.
It came from a booklet described in ACSC as B40. It's a pity that I only had the booklet cover and the one pane ... not the "mail etiquettes" that came with the booklet.
It looks like Type B. Type A is when the dot is further away from the base of the perforation and Type B is when the dot is on the base of the perforation. Enlarged to show the location of the dot. Here is Type A and Type B.
Hi Rob. I did some research, and I think it is a Type A. The first clue is the booklet, which is a B40, and only contains Type A. But, that is only a "belief", per ACSC. It is also possible that my pane and the booklet don't actually come from the same set.
But, I also measured the stamp, and it is 31mm x 22mm, which is typical of a Type A. (Type B is 31.75 x 21.5).
Unfortunately, I also have problems identifying the mesh of paper. According to ACSC, Type A is a vertical mesh, while Type B is a horizontal mesh.
It's too bad it isn't a Type B, as that is slightly more valuable. Thanks for looking.
The bottom dot can be a little deceptive, you could be right, I would tend to believe what it says in the ACSC, the catalogue values are notoriously incorrect, but the information is usually spot-on.
The stamp measurement seems to be correct for a Type A; I also have the same problem identifying mesh and I have a powerful microscope specifically for stamps.
What I do know about the airmail stamp, is the printing process, they were printed using the wet process, the paper was still quite damp; this caused the stamps of the one design and value to have different sizes. In the case of the 1929 airmail, you will find that one type is larger than the other.
When looking at the measurements, even though I agree that the measurement seems correct with Type A, it may not due to the wet process.
You can put that to the test by obtaining a single Type A and comparing it to your booklet pane.
I think it is difficult to classify this stamp as Type A or B only on the basis of the distance of the the dot from the stamp image. This difference in distance is, of course, just a by-product of the smaller amount of vertical shrinkage in the vertical direction. Now the distance between the dot and the image is, by my eye, only about a tenth of the height if the image. This would make the difference between Type A and B a minuscule 0.05mm. So why not just go wth the overall dimensions of the image which gives you a difference of 0.75mm to work with. If what you are saying is correct, That could only be the result of the two Booklet plates coming from different master plates. Given the very short printing run - February to May 1920 and only 15,000 sheets - I think that is quite unlikely.
Do we know the printing configuration of the plates? Were all plates used together to print four panes for the sheet stamps and two panes for the booklet stamps? Another question - why did the size differences occur on the airmail stamp but not on the 1927 Canberra issue which was printed by the same process and in a much higher quantity.