Why do some RR, GTX, Coronet 68-69-70 Speedo lenses have the switch calloouts on the lower lens?

Different Suppliers? There is only 1 part # for the lens in the 68 Parts Book???

I recall using my as bought in '97 lens. when googling pics I see Hemi Cars, AC Cars, GTX etc with either lettered or non-lettering

Dashassem4.JPGRR DASH Chrome letters.jpg

1969 Hemi Charger R/T,
1970 Charger 472 Hemi 6 Sp
1969 Charger Pro Tour Project
1971 Barracuda Convert
1970 440 6pack Superbird,
1968 Fury I Police Pursuit 440 Super Commando 2 door sedan (Black/Blue)
1967 Barracuda Convert
1968 Barracuda Coupe
1972 Charger w 383
1972 Sebring Plus 440-6 Clone
1969 Coronet Pro Street
2009 Challengeer SRT8 stick
1992-1986 Body 2500 4x4 440 stick
1982 Ramcharger 318 Sniper- getting enhanced.
1997 Ram B3500 Van 5.9
1991.5 W250 Cummins- Big Chief