Recent new printings of definitive stamps may soon be replaced, so look out for them now!
I can now show pictures of the 1st and 2nd x 12 booklets on the second type of Security Backing Paper (SBP2). These were printed in late 2016 and have appeared with packing dates of 12-14/12/16. So although this must have been quite a large print run (with packing of the 1st class over 3 days and the 2nd over at least two), we can safely assume that the next print run will be in 2017 and have M17L code.
When the first type appeared Gibbons allocated new whole numbers to the booklets, and I suspect that this time they will only allocate sub-numbers. I have temporarily allocated catalogue numbers ME7a to the 2nd class and MF9a to the 1st class booklets, although this will change if Gibbons allocate new whole numbers.
Similarly the stamps are 2931.6a (2nd SBP2) and 2936.6b (1st SBP2) in our system.
However, distribution from the Swindon Supplies Depot is, as usual, erratic. One correspondent reported that after the latest books had been sold subsequent supplies had year code 15 (and therefore were the old colour). Depending on the ordering policy of your local postmaster, he may never see the new booklets (one branch locally still has 2nd class Large booklets with M12L year code!)
UPDATE 15 March - latest date seen on 1st class packs is 16/01/17, but still M16L.
On 1st class booklets seen so far the iridescent printing is very indistinct, clearer under the phosphor than the plain area, which means that the codes are almost impossible to see. These pictures took some effort to produce:
The 2nd class booklets have much more distinct iridescent printing and the coding stands out well:
The new security printing is darker than the first, so SBP2 is easier to see than SBP1 on single stamps. Singles from booklets will always have usefully large margins of backing paper, but singles from business sheets - other than those from the edges of panes - will be more difficult. As last year, once the booklets of 6 and 4 appear I will have the front cover page, which has no stamps, and will be able to supply to customers on request so that you can illustrate your collections clearly. Look out for a notice on the blog.