Badfrog, It doesn't seem to be military (definately not U.S. military); and is almost certainly civilian fancy dress, probably late Victorian. The V is a mystery, but considering you found it in Canada, the V might have been a subtle way of honoring Queen Victoria?
The Style of the front of this button is 1830s-40s, but since it is a two-piece button it must be closer to 1850s-60s. I do not think it is late Victorian. My guess is mid-century. And yes, a backmark would date it.
Thanks for your input. Unfortunaltly, no backmarks are apparent. So I'll leave it to your evaluation. If I find more on the same site, then I'll ask myself more questions (a coat can only have that many buttons).
Thanks also for the great tips on cleaning buttons. Where would you purshase alluminium jelly, a simple hardeware store ?