C23 Vs C23c Dark Blue Vs Ultramarine?

I came across this attractive plate block. Looking in Scott to see if the double TOP is special. Then I see the ultramarine C23c. The colors are so close, I wanted to assume it wasn't that, just a normal C23. But the more I look at it the more I'm unsure. I see a couple certified C23c stamps online and the color difference does seem to be a lot like what I''m seeing here. I know that the only way to be sure would be to get it certified, but wanted to see if there was any other clues someone might know about. Is the color the only difference? Anything else that might help spot a true C23c?

The single stamp is a regular C23 for comparison.

I expect this is not exactly common knowledge. Well, here's some additional support I see. Looking at Siegel power search I compared C23 and C23c images. Putting aside the color, the lines in the background consistently look thicker on the dark blue than on the Ultramarine. The lines on my block appear fine. Two points in my favor. So anyway, unless someone has any further thoughts this is going to the PF on my next visit. It does have some minor condition issues, gum bends and some disturbance along the top edge - might be mount damage. It was in a crystal mount. Anyway, maybe this is the find of the month!

I have a certified C23c. i'll scan and post probably this weekend.

I came across this article regarding the C23c and wonder if it carries any weight https://www.linns.com/news/us-stamp...erified.html

Is there a controversy with the C23c?

On a separate issue, does a guideline block of 4 warrant a premium?

I asked Bill Weiss if this used block was a C23c and he said it was not ultramarine; just a C23.

Colours on monitors, different colour-naming practices etc etc, but the claimed (and certificated) ultramarines don't like much like ultramarine to me!

Here are my copies of C23 and C23a. The C23c has a 2018 PSE cert. The colors are pretty different on these copies.

Here are my copies. I haven't had the ultramarine certified but it's on my list of issues to send in.

Thanks for the images. Makes me less sure, but will take the risk, and get the PF to look. Cheers.

I was just wondering if this C23 was ever determined to be a "c" variety. I have one that is identical, to include the same plate number for the blue color. Many of the other characteristics of the "c" variety are present, and this one also has the gum creases and minor gum issues. Any info woudl be greatly appreciated. Considering sending to APS for expertisation.

Sorry, but I never did send this into the PF. I ended up doubting it would pass and just put them aside.

The article in the above ebay link is super interesting - thanks for posting!

In the interest of adding some closure to this particular topic, should anyone run into the thread by search as I did just now, I thought I might post the plate numbers for the C23c ultramarine variety. These are noted in the 2nd article in the Ajamian, Rufe, Brittain series "Scott #C23c - the Whole Story," The United States Specialist, July 2021.

Frame (ultramarine) plate numbers: 21948, 21949, 21950, and 21951
Vignette (carmine) plate numbers: 21903, 21910, 21911, and 21912

These were the plate numbers reported by Rumbel in his affidavit concerning the discovery. The authors note that no others have been verified through FTIR spectral examination which the authors promote as the authoritative methodology to identifying this color variant.

The authors also hastened to caution (p. 313) that these plate number combinations also exist with normal C23 dark blue coloration. So the plate numbers above do not identify the C23c variant. They are necessary but not sufficient. But faced with the presence of different plate numbers, one would not expect a C23c.

- Jonathan

R H White wrote the following in 1983 regarding C23c:

"During the past forty years a number of articles or editorial pieces have appeared in philatelic publications presenting the pros and cons on the subject of the blue and carmine normal printings versus the ultramarine and carmine specimens which have been reported.

"The genesis of the story of this stamp has its tragi-comedy aspects when one reads through the literature. As pointless as the continuing debate seems to be, there are some scientific facts which all concerned should consider carefully before offering more opinions on the subject.

"[Viewing my color plate and] Using the nearly solid but finely lined section of the shield medallion at the top as a target, a quick alternation of focus between this area on each stamp reveals a difference in color. The medallion on the blue version is characteristically less red than that on the stamp purported to be ultramarine. The curved ornament designs directly above the numeral 6 also shows this difference in color; the right-hand 'blue' is virtually free of the reddish hue present on the ultramarine example.

" … However, in the case of these two stamps, an 8x magnification clearly reveals the C23 to be bluer (less purple) than the specimen identified as C23c. Brighter ultramarine examples of C23c have been reported.

"Because an unequal degree of inking or a slight discoloration of the paper on the C23c exists, a non-destructive ink analysis was performed. The results are conclusive, if alarming, to those who have had serious doubts about the possible differences between the blue and ultramarine printings. Both stamps have been printed with similar inks of varying composition. The colorant of the normal stamp is a mixture of two pigments, one classified as a mineral blue, the other a mineral ultramarine.

"The C23c specimen is also printed with ultramarine and blue colorants, but there is approximately 30% less mineral blue present. The mineral, a blue iron compound, is quite similar to the blue colorant used in some of the earliest U.S. issues and is found in most blue stamps.

" … Numerous articles on the C23 airmail have appeared in philatelic journals, magazines, and newspapers since its issuance in 1938. Most have revolved around the controversy over the existence of the ultramarine shade. The unfortunate aspect of most of the debate relates not to the facts concerning the ink composition but to the difficulty some individuals have with shades of ultramarine. It has been noted previously that ultramarine blues are 'redder' than iron blues.

"When both colorants are used to affect a certain type of 'blue' color, the problem is intensified. None of the C23's examined is completely free of the ultramarine pigment. Whether intentional or not, the two stamps are appreciably different, both chemically and spectrophotometrically. One can be easily be distinguished from the other, if not by the color perception acuity of the collector, then by readily available color analysis services. "

So it seems from the above article, there can be many shades of blue ranging from mostly ultramarine to a lessor percent of ultramarine. It is not like a completely different ink was used or omitted. Just a varying ratio of two inks. I think that can make a variety very confusing to determine especially when you add in paper shades and the carmine bleeding in.