Canadian Stamp With Overprint

I have been sorting a box of stamps / stamp albums and come across a few of these King George stamps with numbers overprinte on them.

If someone could explain that would be great.

thanks

the system is not allowing me to post a pic, sorry about that.

King George stamp with 4 numbers printed across the front.

They will be pre-cancels. If you don't know what they are, say so and I will give you a brief explanation.
The numbers identify the place where the pre-cancel is valid. I think I have a list here somewhere.

Quebec
0592 - Lennoxville, Canada
0700 - Montreal, Canada
1050 - Quebec, Canada
1142 - Rock Island, Canada
1470 - Saint Hyacinthe, Canada
1810 - Sherbrooke, Canada

Ontario
2186 - Beamsville, Canada
2310 - Brantford, Canada
2342 - Brockville, Canada
2450 - Carleton Place, Canada
2575 - Cobourg, Canada
2980 - Galt, Canada
3080 - Guelph, Canada
3100 - Hamilton, Canada
3340 - Kingston, Canada
3366 - Kitchener, Canada
3445 - Lindsay, Canada
3470 - London, Canada
3800 - Niagara Falls, Canada
3893 - Oshawa, Canada
3900 - Ottawa, Canada
3975 - Owen Sound, Canada
4004 - Paris, Canada
4035 - Peterborough, Canada
4260 - Saint Thomas, Canada
4530 - Toronto, Canada
4900 - Weston, Canada
4940 - Windsor, Canada
4970 - Woodstock, Canada

Manitoba
5099 - Brandon, Canada
5850 - Winnipeg, Canada

Saskatchewan
7120 - Moose Jaw, Canada
7420 - Regina, Canada
7550 - Saskatoon, Canada
7977 - Yorktown, Canada

Alberta
8160 - Calgary, Canada
8360 - Edmonton, Canada
8605 - Lethbridge, Canada
8802 - Red Deer, Canada

Wow, thanks for the typed list.
I have the precancel catalog, but it is nice to have a simple electronic list.

Hope you don't mind if I cut and paste your list?

Thanks from me also, that was way more than I was looking for, I will definately research a few of them.

Tim

Help yourself. I must have had it from someone else, because if I had been copying it from the catalogue myself I would never have bothered to put 'Canada' at the end of every entry!