Please Confirm GB125 Changeling And Postmark?

I confirmed the watermark 30 and the Scott catalog says this should be green but there is a bright blue color changeling. Blues and greens are my worst colors, so I thought I would put it up here for a reference anyway. And I also thought maybe someone might have a story about the postmark and the pac perfin!. Thanks as always - Jeff

You betcha. That's a color changeling alright. You are right on target with that one.

thanks tony

Jeff, the "NPB" postmark stands for Newspaper Branch. This postmark was applied in larger centers for cancelling bulk postings.

Jeff, if the perfin is "PAC", if could stand for Prudential Assurance Company.

thanks mhc99 that wraps it up!

What Scott calls a color changeling, I consider a disservice to collectors.

So here's a tidbit...

There were at least 3 different mixes of ink used to produce this stamp (Scott GB #125), although the production color is the same to the human eye.

The earliest color mix contained lead chromate. To reduce the toxicity, zinc chromate was substituted. However, zinc chromate (yellow component) is relatively water soluble. Removing this yellow component by soaking shifts the color toward blue. So technically, you can say it is a color changeling.

However, when you see a bright blue stamp, what you are actually seeing is a stamp from the 2nd color mix.

Later, the zinc chromate was replaced by another compound (sorry, I don't know what was used) to eliminate the problem. That would be the 3rd color mix.

I don't expect Scott to explain the color mixes in detail. But if you read the simple footnote in Scott, you would think that all #125's could be potential color changelings. In reality, only stamps printed with the 2nd color mix are affected by moisture.

Khj, thanks for explaining the color change in #125. I wondered why this happened and now I know.

thanks khj - jeff