mccune68; OK, you hit on a major problem with how Scott does descriptions with this Issue (another personal pet peeve - they made a mistake in 1943, and it's forever engraved in stone!)
SC#920a is Blue Violet, Red over Black, simple enough. HOWEVER, in printing there is a very big difference between the termininolgy and the imposition (layering) of color between the word "AND" versus ""OVER". Scott, being a both a Printer and a Publisher should be embarrassed in not using the terminology correctly in their write-ups!
Sc# 920 Blue Violet; Red and Black --> Wrong! it's Red OVER Black! This is the most common variety. The colors are not together, they are layered! SO, the reverse printing of this would be BLACK OVER RED, correct?? But, how does Scott list it...they list it backwards (Red/Black!)
Sc# 920a Blue Violet; Red over Black -->This is a TYPO! The REVERSE of the ABOVE is BLACK OVER RED!!! This is a scarce printing and is unpriced by Scott! Scott Editors repeat the same mistake for 920b & 920c; at least they were consistent.
To understand printing basics on this stamp, I'll explain how color was laid-down on paper to rotary printing. The other Blue violet border is engraved, the Inner Flag by Rotary printing.
Sheet Layout 200 Subject Layout Type 1
or 400 Subject Layout Type 2
The "Country Name" was printed with a separate Linotype Printing Plate residing in the 5th Roll/Plate position on Press. (Exhibit pjs 2-5 above)
Rotary Print Color Imposition would have been (C/Y/M/K) with the Cyan Roller omitted. Print color was laid down in the following print order:
Correct Printing: REVERSE PRINTING:
1. Yellow (base) Yellow (base)
2. (omitted) (omitted)
3. Magenta Black
4. Black Magenta
5. Linotype Magenta Linotype Magenta
How To Check For Reverse Printings:
Since I haven't created artwork for the Denmark Flag, I am using the Poland Flag to illustrate "how/where to" check to verify "Reverse Printings" on these issues.
Here are the key checkpoints to the correct identification of black ink over bright red ink print variety:
1. Check the lower left corner of the flag, where the flag meets the flagpole (also known as the bottom hoist end), as shown in Figure 1. The black ink should overlap the bright red ink, where the flag meets the flagpole.
2. Check both the left and right sides of the flag, where the bright red and white fields meet (Figure. 2.) Here, overlapping color or color slightly out of registration (alignment), horizontally or vertically, will make it easy for printing identification.
3. Check along the bottom black shading row dashes along the bottom of the flag (Figure 3.) The black ink should ride over the top of the bright red ink.
4. Check along the top black shading row dashes, where the red and white portions of the flag meet in the middle (Figure 4.) The black ink should ride over the top of the bright red ink.
The way the color was played down on Sc# 909-921 was: Frame + Y/C/M/K + Linotype ( or Blue Violet + Yellow/Cyan/Magenta/Black + Linotype Color Plate, in that order, first to last).
Of course, if you think you have a Reverse Printing it's best to get a Certificate from the Philatelic Foundation or the American Philatelic Society for your find.
Hope that explains the confusing Scott write-ups under the Overrun Countries Issue; I hope I haven't made it harder to understand..
N.B.: The Denmark issue also has a Double Impression of the Black Flagpole. You'll have to wait for the Denmark Book to learn "why" or how this happens? (Hint: Has to due with the fact there was no Cyan Plate, which is also how I think they ended up with a Reddish-Brown Pole.)