Same US Stamp-Many Color Shade Differences??

I have been away from collecting for 20 years, so I am a little confused about this. Are the differences in the shades of blue of the Rx on the mortar and the differences in the color on the pestle(they slightly missed putting the color on the pestle in the left stamp, top row) from different printings- or from being printed in different places?? I have been reading through some of the forum messages, and was wondering about this. There seems to be about 7 different shades with different "shading effects" on them in the stamps I found in the loaner book. Would someone please help me out on this?



rockinrobin....dazed and confused

It is called a color shift and this stamp is known to have several that range from the blue to the orange. There is a long list of US stamps with a color shift. I believe if the are MNH they have a pretty nice value though. The used brings the whopping total of 20 cents catalog value though I could be wrong.

Here I found a MNH for you to look at.





Image: colorshift.jpg
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Thanks for the info mkfarm! Interesting color shifts!
Gussyboy1