i got an envelope in the mail today, and on the return address it said 

H ¼ º º EDDNs

in what looked to be typewriter font. What could this mean?


There was nothing in the envelope. It seemed awfully suspicious...

I don't feel its actually a "coded" message as such. You mention that
it is a typewriter font. Very likely he forgot to unlock the 'caps'
mechanism on the typewriter while typing the  ¼ º º section. But its
hard to guess what the characters are in the lower caps of the ¼ º º  
as they vary from typewriter to typewriter model.

Very likely some numbers? But people do write strange messages using
numbers and characters. For instance H34L7H is also read as HEALTH !!

cheers!

This could have been printed from a computer.
The computer may have had problems communicating with the printer at
the moment that was being printed and garbage came out.