It all looks pretty dull, but there is a, vaguely interesting, story here.
The style of having a p-knuckle with a concealed p-pivot bolt is generally thought of as being part of Shimano's assumption of world dominance. During the 1980s Shimano redefined the rear derailleur. Indexing, stylish paint finishes and a smooth aero look that included a concealed p-pivot bolt - they were all seen as components of Shimano's irresistable tsunami of innovation. The first Shimano derailleur to have a concealed p-pivot was the achingly beautiful 1986 Shimano Santé. But this patent, held by ugly, uncool, Simplex dates from 1984. Interesting!