There are a total of 5 sheets of 50 in my custody. As you can see, some of them are too big for the scanner. I am also enclosing a scan of the article by W H Adgey Edgar which was published in the Philatelic Magazine in June 1948. But I wonder whether the Die II that was mentioned is actually a forged overprint.
The bottom overprint has Die II and the spacing between and the characters are irregular and not precise. I think this is a fake overprint. I have not seen an overprint used like the one depicted in the Stanley Gibbons and some other catalogues. Here, the first character has equal legs with the left connected to the next character. The explanation could have been that they did not show the real overprint to prevent copycats. But it is also very important for collectors to be familiar with the structure and format of this overprint as fakes both old and new are abundant.