Switzerland Scott #b43 Printed In Two Colors?

According to the Scott catalog this Pro Juventute stamp from 1927 was printed in one color, red. The other stamps in the series are each printed in two colors. In the following scan, the stamp on the right appears to be printed in two colors, red and black. It could just be toning or a color changeling but if you look closely there are instances of engraved lines side by side where one is just red and the other looks like red and black. Do any of the specialized catalogs (Zumstein, Michel, etc.) mention a two color variety?

It very much appears to be oxidized.

That was my first thought too but it seems strange that there would be two adjacent lines of ink, one oxidized and the other not. Maybe I just need to look at a few million more stamps to learn the vagaries of oxidation. :-)

It looks that Rogdcam is utterly right :)

Yup. My copy of the stamp was printed in one color only

Peter

As you look at more stamps, you will likely find:
Oxidation seems to start in areas where the ink is heaviest/densest. That certainly seems to be largely the case here.

Oxidation is not necessarily uniform unless the whole stamp has been affected.

Presses of this era that printed engraved stamps could only do one color at a time. This is definitely not a two-part engraved design.

That is not true!

The 2nd Panamerican Postal Congress was held in Mexico City in 1926. The commemorative series contained a 1 Peso stamp that was very special.


For the first time in the world history of stamp printing, a BICOLOURED recess stamp had been printed from ONE single plate using an advanced way of inking. It took 12 years for next postage stamp to get issued in a similar manner printed by the PWPW in Warszawa in Poland.

Thanks Galeoptix
Always great to learn something new on this site.

Sulphurization/Oxidation

http://www.stampsmarter.com/learnin...idation.html

Thanks everyone. Regarding the article on removing the oxidation, in this case I actually like the looks of the oxidized stamp better!

Thanks for the correction! So which Polish stamp was this? The philatelic exhibition souvenir sheet?

Oxidation has enhanced the aesthetic appeal of this stamp.