New style sight
In 1967 S&W came out with a different design for the rear sight leaf (shorter I think) which necessitated relocating the hole for the screw that held it down by by moving it about .110" toward the back. These new sights were added to all the K-frame adjustable sight guns in 1967 .
Following is a list of all the dash changes for the 19. enjoy
Engineering changes were designated with a "dash-" number after the model number. The engineering changes are as follows:
19 - 1957: Stamping of model number.
19-1 - 1959: Change extractor rod, right to left-hand thread.
19-2 - 1961: Cylinder stop changed, delete triggerguard screw.
-------1963: Introduce 6" barrel.
-------1963: 50 manufactured with 2.5" barrel, serial range K544672-K544721.
-------1966: Introduce 2.5" barrel as standard.
19-3 - 1967: Relocation of rear sight leaf screw.
-------1968: Delete diamond-insert grip.
19-4 - 1977: Change gas ring from yoke to cylinder. (not really an "improvement". It did make it slightly easier to clean if you had heavy leading, but basically was a cost-cutting measure.)
19-5 - 1982: Eliminate cylinder counterbore.
