Here's some pix & stuff I think I know about taillight lenses.
I looked through a pile of old lights over the years and you'd be surprised how many old repro lenses are out there.
...maybe in the neighbourhood of 20 fakes, to one original.
Now before you get excited you must factor in that 4 out of 5 originals will be broken in half
You might hit a good original after turning over 20 repros.....or you might be like me and find 1 in 100.
Hey somebody has to make these statistics
1) The dead giveaway of a repro, is the dyed or painted backing that usually flakes off with your fingernail. Painted areas are usually chalky with age.
The new repros I see, have all been dyed.
The texture inside the lens is different from originals...it looks & feels "drier".
2) Once you have the real thing in your hand and see the dyes bleeding together within the actual glass, believe me...you'll know it!
The original lens is thicker than some of the repros. It shows irregularites, yet feels polished & smooth.
I have no repro lenses in stock, although here's a couple originals that turned up in some ratty & dented taillights covered in years of crud.
It took bleach and a nail brush to shine em up.