Scott #657 - "The Plunger"

Hi..noticed this abject on the top right corner of my Scott #657
block..has anyone seen this before..thanks.

That's a "litho" bubble, sometimes called a "donut". They are the result of some cleaning-type fluid left on the printing plate (not properly wiped off between print runs).

Many Canadian stamps have them. Sometimes they can be quite large. They can occur on more than one sheet (in the same location) in any given print run, until the plate is properly wiped.

It would be considered an EFO/freak, not a constant variety - but collectors do pay a premium for them sometimes, it will depend on the size of the bubble, the stamp and location on the stamp.

Nice block.

Thanks 3Dadeo, I hadn't heard of that before. learning, learning.