A photo to show the three different types of clip-screw/cap-tassie on my Parker 45s.
‘Inverted-cone’ or ‘conical’ tassie, on my Parker 45 ‘Flighter’ BP, which I believe to date from the late 1960s.
‘Dimpled’ tassie, on my Parker 45 ‘Flighter’ FP from the early 1970s.
’Dished’ tassie, on my Parker 45 ‘Flighter’ FP from the late 1970s.
Both the ‘dimpled’ and ‘dished’ tassies appear to have been in continuous production after 1970.
I cannot believe that any company would invest in two different types of tooling in order to make the same small part, and so I suspect (based solely on a total guess) that the ‘dimpled’ tassie is a ‘dished’ tassie that has been machined to create the dimple.
Or, if you prefer, that the ‘dished’ tassie is actually a part that was intended to be machined in to a ‘dimpled’ tassie, but which was accidentally released in to the world in an ‘unfinished’ state.