Here is a perfect example of the difference between the two CDs

While I know most people will tell you it's concave vs convex I would have to disagree (to some extent at least)

on the left is a definite CD 133 embossed (F-CROWN) PATENT / DEC 19 1871 and nothing on the rear It's about 4" tall, very heavy glass and very crude looking mold.....It almost looks like a convex 132....

On the right is what I call a "Transition Mold" 133.4

It's embossed (F-Crown) PATENT / DEC 19 1871 (R-Crown) 3 (R-Skirt) A

It is about 1.5-2 cm shorter and has an odd pointy dome (I believe it was a mold defect)

I will try to get a line up off all the mold letters in the 133.4s but I believe this A mold is the only one with a pointy dome the rest are the bulbous ones we more readily see.