There is a lot of good information at the National Button Society web page: http://www.nationalbuttonsociety.org/ I especially like the Button Gallery page and refer to that a lot when trying to determine what kind of button I have. If there is a back mark or lettering you can often search on that to learn the origin of a button.
If you join the National Button Society, you will have access to decades of button articles and photos. These archives surpass everything else that is out there.
