Atlanta Trial Color Proof Cards And P4 Proof Cards

How do you differentiate the Atlanta trial color proof cards and the P4 proof cards with the same or similar colors?

For example, the official stamps for dept of state are dark green and their Atlanta trial color proofs also contain the green. How to tell the difference between O57P4 and O57TC4d? The color difference is subtle.

Another example is the official stamps for the dept of interior which are vermilion in color and their Atlanta trial color proofs also have a similar color scarlet (eg O19P4 and O19TC4b). I have two proofs in attachments, the left one is slightly thinner than the right one, but it's hard to tell the color difference. Is one of them O19TC4b?

They both look like O19P4. The Atlanta trial color O19TCP4b, scarlet, has a rosier tone.




The State Department card proofs are much harder to differentiate. here is an O65P4 and an O65TCP4d.

Thanks! If you have both, could you please kindly comment on the thickness of the cards? Because I encountered other Atlanta cards which do not have a similar color counterpart in P4, they are thinner than P4. That's is why I thought one of my card in the photo is an Atlanta card, because the thickness difference is obvious. One is much easier to bend.

In the following article, it mentioned "thin card" for Atlanta cards, but didn't use the word "thin" for P4. I wonder if the thickness is indeed a real difference.

http://www.rpastamps.org/presentations/usproofs

Yes, the Atlanta Proof card stock is thinner, how much thinner I couldn't tell you. But noticeable, not as rigid as the P4s are. There were possibly six printings of the P4s.

http://chronicle.uspcs.org/pdf/Chro...14/12898.pdf

@littleriverphil

Thanks!