Thanks to our correspondent, another Ian, who reports:
There is a very short band on the bottom stamps but a full band on the top stamps. I understand that two books were found -- which is not to say that there may not be 10,000 more out there waiting to found! As this is a plain (non-cylinder) book, I'm not sure if these are from the recent reprint from grey cylinder W3, but I think that they are.
Unlike more recent sheet-printed stamps, the phosphor on these and the 40gr booklets was printed on the central matrix as well as the stamps, meaning that only the bottom row could have short bands at the foot, and only the top row could have short bands at the top. Even if this is a new printing, it would make sense for the phosphor cylinder on books of 4 to continue if possible.
Here's a picture of all 4 stamps: