xiusudra
You raise an interesting point which I had been wondering about, i.e., "Why U.C.?"
In 1841, the provinces of Upper Canada (now Ont.) and Lower Canada (now. Quebec) were joined to form the United Province of Canada. What had been Upper Canada was now called Canada West (C.W.) and Lower Canada was now called Canada East (C.E.)
Here is a cover mailed to Montreal in 1845

Note that it is addressed to Montreal, Canada East

Here is cover mailed to Woodstock, Canada West in 1844


So, why U.C. when Welland was in Canada West (C.W.)?
The firm of David Garden Berri of England manufactured handstamps for the Canadian Post Office Department. Berri provided broken circle handstamps from 1857 to the late 1860s. Until 1860, the Post Office Department instructed Berri to produce handstamps with the letters U.C. (Upper Canada) or L.C. (Lower Canada) even though these terms were obsolete since 1841. In 1860, Berri was instructed to produce cancellations with the letters C.E. or C.W. which according to the Post Office Department was the legal designation of the sections of the Province.
Berri Broken Circles Made Before 1860U.C.
L.C.
Berri Broken Circles Made From 1860C.W.
C.E.
To conclude, I had wondered why the Welland handstamp had the letters U.C. (Upper Canada) even though Upper Canada had become Canada West in 1841. The reason is that the Post Office Department did it that way! (I will be try to find out when the terms Canada West and Canada East became legal designations)
By the way, I recommend that anyone interested in Canadian Postal History consider joining the
Canadian Postal History Society.
http://www.postalhistorycanada.net/php/index.phpOn-line membership is only $15.00 per year and provides access to its excellent Journal:
http://www.postalhistorycanada.net/.../journal.phpAll 149 issues of the Journals have been archived.
The information used for this posting was obtained from this article:
The Broken Circle Postmarks of Canada, Scrimgeour, K. Gray,
PHSC Journal Whole No. 42, pg. 35, Jun 1, 1985