I wasn't online when you posted this, or I'd have pounced.
Wolfgang is correct, these figures were cast with molds made by Schneider Bros. of Leipzig, Gebrüder Schneider, in German. They operated from around 1890 up through the end of WWII, though it's been suggested that they lasted into the early years of the DDR. Their molds were sold here in the US by various agents, most notably Henry Schiercke, and also copied by Sachs and others. Also, they were reproduced in more recent years by Höhmann in Cassel (I bought many of my molds from him) and Greiner. It's possible to identify and date the molds, by the metal from which they were made (the original molds were bronze, later reproductions are in a zinc alloy), and from markings, in the case of Sachs' copies (his mark was an "S" with an arrow through it).
However, it is nearly impossible to date any figures cast with such molds, precisely because they were sold to hobbyists for casting at home. That meant that all varieties of alloys of lead and tin were used, with varying results. I could take old tire weights, melt them down and cast some Schneider figures, and in a couple of years, they'd look like they were cast in 1890, because of the poor quality of the metal. Good quality alloy, with a low percentage of lead, and cast using the original molds, will give crisp castings, like the ones in John's photos. Poorer alloys, cast using some of the copied molds, like those sold by Castings in Washington state, will produce castings with softer detail.
It is possible to date those Schneider figures, produced by any of those homecasters who sold their figures and boxed them, tied them to cards, etc, and operated under a trade name. In Richard O'Brien's books, there are some examples of such figures. In those cases, where years of operation have been noted, it's possible to date the figures.
Having said all that, they have a definite charm. I have a collection of them, from my initial forays into casting, and I like them, for their classic toy look. I've got some original molds, some zinc molds from Höhmann, and some of the American copies sold today by Castings.
If you paint, feel free to strip them and repaint them. You will not affect the value in any way.
Hope that helps, prost!
Brad