Just put new glass in the front of my car. While going through the side glass to match the manufacturer, I found that one of the rear windows was marked differently than the rest.

Three of them are marked:
LOL Safety Flo-Lite AS-2 TV DOT 15 M71

One is marked:
LOL Safety Plate AS-2 UV DOT 15 M51

Are some tinted? I can't see a difference looking at them. Any help would be appreciated.

If there's a difference, you'll see it. The tinted is sort of green when held up next to a non-tinted glass. My right side vent window is non-tinted, but the rest of my glass is tinted. The difference is obvious.

I cant see a difference.
So are we saying that the markings are from different because they are from other years?

LOF is likely what you meant ( Libby Ownens Ford Manuf. )

AS = AMERICAN STANDARDS ASSOC. OF CLASSIFICATION

AS1 = Windshield Glass
AS2 = Body glass

M51 Manufacturer's Model # ( Body Glass )


None of these are date codes, so hard to say if any is from another model year...but point is...glass got coded according to where it was, windshield vs. rear, side, vent, etc... also you may find PPG glass for vents...UV would seem to indicate a tinted ( ultra violet glass )

I was thinking that the UV was also indicating Ultra Violet but if tint is obvious, I'll be darned if I can see it.
66 Mystery... you said M51 is Manufacturer's Model # ( Body Glass ). What is M71?

Try this little trick: Put a sheet of white paper behind the glass in question. You will be able to tell a difference in the white paper if the glass IS tinted, no difference if the glass is NOT tinted.

Very little difference.
I even put them side to side and could only see a slight difference. The one I thought that looked like it had more that the other was the one marked TV. Go figure.