Sinclair published two versions of the dinosaur stamps. The earlier versions are the two-tone stamps. The second issue was in 1959 and was the multi-color stamps. The earlier stamps had "Sinclair" printed on them. The second did not, at least on the set I have.
Also, the first issue apparently involved two albums. So far I only have the second volume, but have seen the first so am keeping my eyes open.
Thanks to all for reviving a very old memory. When I was very small my dad took us all to see the life size Sinclair Dinosaurs in the parking lot of a Pennsylvania shopping center. I remember being awed by the giants and walking through a tent full of exhibits where I got no stamps but I still have my souvenier plastic ankylosaurus. If you google Sinclair Dinoland you can see it in all its glory. 1964? really? I'm so old.