Great post Warspite!! I love the period picture!
It is fascinating that they continued to sew the rear closure strap on diagonally and without a brass tip on a carrier manufactured to the new specs. It is also interesting that they didn't modify pattern 1919 waterbottle carriers (which were designed prior to the 1921 modification). Khaki (not blue-gray) Pattern 1925 waterbottle carriers were also top closing since they were designed after 1921.