Question About GB Postmark Penny Red Cover?

In my humble opinion, it is an attempt to make a cover by way of sticking to it a defective stamp. The envelope must have had a different stamp (lost or soaked off; could have been critically damaged, thus removed), a kind of trace is still visible of what could be the original obliteration. This one looks a substitute to get rid of the otherwise unwanted stamp (look at the missing perfs and frayed corner). The cancel does look strange too, yet it can be real.

I looked through my period cancels from GB. All are tied and include the CDS. My opinion is the was stamp was added somewhere down the line and although it probably is used it just wasn't on this cover.

Thanks Guys.
The cover sure looks dodgy and 99% sure the stamp was added afterwards, Never will know what happen. Maybe some school boy did it years ago.
The postmark also seems very suspicious with the way the 66 is very blocky.
I decided to sell it as a piece of postal history as the contents make for a great read.
I did mention the fact that the stamp and cover are not tied in the listing.