I was going through a bunch of circulated, not fresh from the BOC $100s today and there were a run of notes that stuck out from the bunch.
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Sorry the picture isn't any better, but the notes stuck out as the lithograph portions were significantly lighter in colour than the rest of the notes. Normally the lithographed portions above the portrait seem to have a greenish tinge, while these ones were just light brown. If you look closer, the vertical lines that give the background a greenish tinge are missing on the bottom note.
They were from the EKC prefix, I found 2 runs that were approximately 30,000 notes apart that all had the identical odd colour.
