Another member sent me a link to that note earlier... I've heard tales of bleaching a note to remove the ink. Just think of some counterfeit banknotes: the more decent ones are made by bleaching US $1 notes, then printing a $100 note on top.
Also, as with many other "errors" seen, such as missing serial numbers and the like, the process of removing the serial numbers often destroys the note reducing it to a grade such as G/VG, and similar to what we see in the above images.
It is very difficult to prove the authenticity of an error of this nature. If the note was UNC, it would be easier to detect any traces of the original ink or intaglio "embossing", but with a note in this poor of condition, it is nearly impossible.
Note also the serial numbers leaching through to the back of the note. This is often a side effect of being subjected to chemicals.
Venturing out on a limb here, I would suggest that this note might also smell fairly bad.
Logged
BWJM, F.O.N.A.
Life Member of CPMS, RCNA, ONA, ANA, IBNS, WCS.
President, IBNS Ontario Chapter.
Treasurer, Waterloo Coin Society.
Show Chair, Cambridge Coin Show.
Fellow of the Ontario Numismatic Association.