That is just crowns, no types ('middle' set) ... if there's no wmk
it's the later set, if there's an "E" or "R", then it's first set.


Yepp, near enough!

'Early' sets (1955-58) have Crowns + E2R in alternating patterns.

'Middle' sets (1959-68) have smaller Crowns only, closer together,
in a 'diamond' formation.

'Later' sets (1967-68) have no Watermarks (Bradbury-Wilkinson)
and are printed on paper with finer, even fibers.

Most of the Watermarks are easy to see by adjusting the viewing
angle, in direct sunlight - the best observation lamp there is (and
John has one helluva lot of sun where he lives)!

David.