To be sure you would need to reference a Canada Railway cancel catalogue (Ludlow is the older one) as sometimes a simple railroad changes it's postmarks over time.
Example, could be (guessing) TOR.& OWEN SOUND R.P.O. or TORONTO & OWEN SOUND R.P.O. .
The & (and) character is usually found between station names.
R.P.O. = Railway Post Office.
708 = I think this would be the train number. So a train running in the opposite direction would be #709 perhaps. Sometimes there is a cardinal direction stated like E (for East), N (for North), etc, that indicates the general direction that particular train is running on that section.
No 1 = I think (faulty memory here) that this is the cancel number on that mail car or coach (wagon), in the case of multiple clerks and cancels being used.
Ah, an
ebay listing had a similar one:

From the description:
Quote:
Canada
Railway Post Office Cancel
Ludlow - #O-391 (4)
TORONTO & OWEN SOUND R.P.O. /No.
Type 17A
Period 1905-1955
Train #708
Rarity Factor 85
on #233 3 cent carmine King George VI
Jun 3, 1937 Postmark
Here is another I found (poor quality scan) of the direction being North (N) instead of a train number, and the clerk or cancel hammer being No 3.

The CAFC-5051 is a Canadian Air Force (Command?) base #5051. I can not find the list I had on which base is which place but it was referenced or mentioned on SCF quite a while ago.