#50 And #56...where Are They?

Today I received a small packet of classic stamps in trade, and there's a couple that have me stumped. The sender labeled them all for me, and I trust him. There are two that I don't know what to do with. They are labeled Scott #50 and #56. My Mystic album skips over all of the 40's and 50's, and there's really nothing about them in my Scott catalog. Can anyone enlighten me? Where do I place them?

Those are now in the proof section. The first page after the essays, just before the proofs. They are scarce to rare, so it's fairly unlikely that they will be those items.

Thank you, revcollector. So what do I look at to determine what they are?

The catalog will explain it. They are know as the August Issue, they are really essays with small design differences to the issued stamps.

I did the whole swedishtiger.com thing. Turns out they are #156 and #187. Fair enough...I still didn't have them.

Scott 56 is now known as 65-E15h which can be located in the 1861 FIRST DESIGN ESSAYS AND TRIAL COLOR PROOFS section of the Scott U.S. Specialized Catalogue. Don't know what 50 may be.
In a similar vein, my old album still has spaces for Scott 66 (now 66TC6) and Scott 74 (now 74TC6) ... both are in the TRIAL COLOR, DIE AND PLATE PROOFS section.

Here's a pic. How did I do...156 and 187?

I had a very good historical explanation of the 50, but the image posting shot that down entirely. Nevermind.

Maybe. It's hard to see if there are the secret marks or not from the scans. It sort of looks like there is one in the 1c but maybe that's just part of the cancel. Same on the 10c. I think I see the secret mark there. If either of them have it then those would be other Scott numbers. Neither 156 or 187 have secret marks. The bank note series is generally very tough and sometimes comes down to paper type etc. If you can get a close up scan of where the secret marks should be that would help. (The swedishtiger site tells you where to look for them.)

I checked for the secret marks. The 1c has one, the 10c does not.

The gentleman who sent them to me said that the numbers he wrote down were partially rubbed off. He said they are 150 and 156. Makes sense now.

The 10 cent is 209.

Rogdcam...can you explain what tells you that?

I agree with rogdcam ... 209. Micarelli's book has good explanation of some of the distinguishing details.
Added: One of the experts on this forum once pointed out that the borders on 209 are quite a bit darker brown than those on the earlier 10-cent Jeffersons. This was not in Micarelli.

I used the identifier on the Swedish tiger website, and came up with 187 instead of 209. Where did I go wrong?