Hi boyz
I've seen that a number of times down here in Atlantic Canada. The Coin Cabinet in Moncton has/had a number of low-value post- and SWW Canadian badges with this darkened shading added. Regiments and Corps badges. They were all on the same thin carboard card with ballpoint pen annotations. Maybe 15 or so per card and a couple of cards. I have seen those cards cut down around the individual badges since. As well, at our Shows, I've seen a few of these loose in trays of vendors over the years.
One of our collecting society members, and I cannot recall which, told me that he had determined that it was India ink.
The Westies attached is the only one I have so I can't give you any other examples. Especially at this time of no Shows.
No idea as to their origin but I saw the first ones probably around 2005.
Hope that is of some help.
regards
Darrell