GG: "7" in the header

["Junichi Miyazawa" <walkingtune@bigfoot.com>]

As some of you know, 
I am now checking and polishing my translation of GG letters.
In the headers of many of GG letters(typescripts) from 
the St.Clair Avenue, I found  number "7":

-------

                 110 St. Clair Ave. W.
                 --------------------------
                                7

                                                                   [date]
[addressee]

Dear [xxx]:
.........................................................................
........................................................................
-------

What does "7" stand for?  Is it the room number of
his penthouse in the 100 St. Clair Avenue West?

Do let me know.  Thank you in advance.

Regards, -- Junichi

****************************************
  Junichi Miyazawa, Tokyo 
  walkingtune@bigfoot.com
  (alias for: farnorth@mbc.sphere.ne.jp)
****************************************
  http://www.geocities.com/Vienna/3739