The bottom ones were used on early ('78 & '79?) models in the US. The upper ones were used after those - on through the SP II IIRC. The early ones consist of just the signal and surround, the later ones have more pieces: signal body, mounting bracket, surround and a gasket.
From the research I did when I was looking for early bits, I found that the signal was used on several Italian cars (Maserati and Fiat 850 sedan) but the lens was sometimes clear in those applications. They were also used on Ducatis. Rather difficult to find.