You might visit the websites of the current type publishers. They often will specify the year a font (or an earlier version of a font) was created. This will of course give you initial dates of use, but fonts created 100 or more years before 1870 might still be in use.
Rather than microfilm, you might find that a university library is a good hunting ground for old type. A long established library will have many books on the shelves that are over 100 years old.