Any Ideas? Heller School Of Magic W/Perfin Cover

Found this in a estate lot. I have no idea what is going on here. The return address indicates a "Heller's School of Magic" in New York. I have been unable to locate this on the internet searches however.




The stamp is what really has me stumped! The value looks British of 2/0 (Shillings/pence), and doesn't actually say anything of origin of country, it does say "Mayor's Court" with a nice coat of arms.
The stamp contains a perfinned pattern of a large "M" and a second letter partial. (I have enhanced the perfin in red)




Any of you have any ideas, other than this is a fabricated cover (my leanings). Anyway, it is an interesting thing. WIll keep it, don't know why however....

Help appreciated.

London... and someone with Barefoot Catalogue can help. PDF file.
Perfin M.C.
http://www.perfins.org/Bulletins/20...5/pix/05.pdf

Thank you for the help!

This is quite possibly the namesake of the Heller's School of Magic (New York) -- George Washington Heller (1860-1928):



http://www.geniimagazine.com/magicp...r#cite_ref-0

Looks like the stamp is on another piece, and was added to your envelope later.
I think it's a revenue stamp of some kind, used on official documents.