Here is how another hobby handles an alteration.
This was I think 3 months getting a certificate, at $35. I didn't know the cancel was fake, but the PF did. I'm still very happy with it, as it's a new discovery. (Not my discovery, but I believe this was the first copy certified) I don't know if they needed it, but I sent a copy of the article identifying this as a foreign entry along with it.
The fake cancel may have been added for a couple reasons. The stamp may have had damaged gum, or been stuck down so the gum was removed. A nice used copy probably sells faster than an unused copy that's got a problem like no gum. (decent price reduction). It's also possible that there's a very light cancel in a common color, and the blue fake was added to increase the value( decent addition to catalog value for a blue cancel)
