I really shouldn't have posted my reply earlier as it was near 5 AM and I hadn't been to sleep yet. When I started that post I had something in mind, but by the time I finished it, *POOF*, it was gone. It wasn't until I was already in bed that I remembered what it was I was going to say.
First, a reference to "turn mold bottle produced in the mid 1850s" on the page link below seems similar to your bottles.
http://www.blm.gov/historic_bottles/References.htm
But, considering your bottles are likely from England, or somewhere else in Europe that uses the metric system, (Canada didn't use the metric system back then, but someone from England might have produced the bottles here using the metric system). The 500, or 600 on the bottom of the bottles should refer to the volume in milliliter's. For definitions of milliliter see:
http://www.google.ca/search?num=100&hl=en&safe=off&q=define:milliliter&btnG=Search&meta=
This page looks interesting and there seems to be bottles with similar bottoms on it.
http://www.blm.gov/historic_bottles/bases.htm
The "turn-mold bottles (also called "paste mold")" looks like it might have been the type to make those bottles of yours. If so, then you would have rare ones because they seldom had embossing on the base.
I would guess that your bottles are either produced by the method above, or by the "snap case and sabot", (I would guess this is how they were made), method also explained on that webpage, (I'm not sure how rare embossing is on the bottles produced using the snap case method). Either way, I would think they both have monetary value. Try searching the bottles section on eBay using the terms: and
I checked eBay for "snap case" in the bottles section.
http://search-desc.ebay.com/search/...action=compare&copagenum=1&coentrypage=search
Then I checked for "turn mold":
http://collectibles.search-desc.eba...atitleZQ22turnQ20moldQ22QQsubmitsearchZSearch
And "paste mold" didn't turn up anything.
Another interesting site, with bottle dating info and a small but good links page, (once you highlight everything so it can be read):
http://www.knology.net/~fullcircle/DigGide.html
Google images is another place to look once you have an idea what your looking for and what search terms to use.
Good luck!
F.