Directory 35

I may have asked this one before, so if I have...
Does anyone know what this auxiliary marking on a US cover sent to Canada would mean? Directory 35. Pictured here in the lower left corner of the cover (indicated by arrows).



It appears the letter was re-directed. Could it be a reference for the postal workers to reroute the envelope?
Help!

I have a number of covers like this that I found in my grandfather's collection, all sent from the same friend in Ottawa to my grandfather. As far as I have been able to find out, there are two possible explainations for these markings. The first is probably the most likely as it is related directly to the post office. When a postal worker added information to an address, they had to reference the location, so "directory 35" would be page 35 of the Toronto postal address directory. I could not find an example of a Toronto one, but here is a link to one for Madison City.

http://www.google.ca/url?sa=t&rct=j...FjAGOAo&url=http://images.library.wisc.edu/WI/EFacs/MadisonLocHist/MCD/MCD18712/reference/wi.mcd18712.i0010.pdf&ei=36aBT6bvM6K02gXy35H0Bg&usg=AFQjCNEQ6RmsvIzrfCw6cBaD9DHEhkK_sg

The second and less likely option is that the "directory" stamps (most of mine say "directory 12" or "station 7") were already on the envelope before shipping, and are inter-office mail directions for a large office building. They work sort of like an extension on a phone system, if you needed to send a letter to someone or to a department in the building it got stamped with their pesonal number from the postal person on your floor, and was delivered via the mailroom service to the correct person. I guess this is the what was done before email. I guess rather than throwing the envelope away, some people recycled them.

Mail which could not be delivered because of an incorrect or insufficient address was not automatically sent to the Undeliverable Mail Office. Attempts would be made by the local post office to determine the correct address. Telephone directories as well as other lists were used for this purpose. This was referred to as "Directory Service". Handstamps were applied, often with identification numbers, to indicate that a search was required which accounted for the delay in delivery.

The numeral 35 did not refer to a page in a telephone book.

lorddenning

Perfect. Thanks to you both.
And...Welcome, Me Lord.

So, five years later, we revisit this page.
Here's a postal card from Pakistan, circa 1948 judging by the stamp design, receiver cancel on the back indicating it was mailed in 1956 to Vancouver. Stamp missing from the front obliterates half of postmark.
But here's another example of a piece of mail redirected and a 'Directory' auxiliary marking.

"AskPhil"

Directory markings: postal markings that indicate delivery attempts, stating reasons.