US Scott 1684

What was the reason for the extra black plate # for
US Scott 1684 as shown on this block of 10 ?
The stamp was printed using the 3 process colours, cyan, magenta,
yellow, plus black -----> the CMYK color model so why
two virtually identical black plates?

I have seen this on some L.B.J. stamps I have, where the 2 blacks are, they go reverse the other way with the other 3 colors. From the inside out, black being the start points. Trying to find them to post. Respectfully, Gary

According to the USPS Souvenir Page provided for this issue, the stamps contain five plate numbers, representing the following colors:

1. Yellow
2. Magenta
3. Cyan
4. Black Tone; and
5. Black Line



My guess is that "black tone" was the intensity of black used within the design; "black line" probably represented the black printing used for the lettering and/or date.

Thanks wt1 for locating and posting that
information which clears it up, I guess.

Still, wouldn't one black ink have sufficed?

I wonder though maybe it had to do with the viscosity
of the ink and not with the shade of black?

You could be right. Even taking a modern US stamp with a letter followed by numerous 1's (to depict different colors) there are a few that use two "blacks" ... one for the stamp and the other for the so-called verso-text outside the stamp (i.e. printing on the selvage and/or back of panes, etc.)

Although I don't think there was any printing on the back of the Scott #1684, the stamps of that period did have "MAIL EARLY IN THE DAY" and the Mr. ZIP logo in the selvage. It could very well be that the black needed to print those phrases and/or logo would need to use a different shade of black than that used within the image on the stamp. (Just a guess on my part.)

The middle block of grey in the two blacks is noticably different in shade

Yes Chewie, I agree with you,the middle bar of Plate 36994 is slightly .darker