Belgo was a Belgian company that made white metal figures in the 1980s and early 1990s. Since they've gone out of business their products have become extremely rare. I have four GIs and their quality is not as detailed as resin but quite decent nonetheless. White metal figures should be washed and seam lines removed with a file or sharp hobby blade, and then primed before painting.

I'm sure this is a very incomplete list; if anyone has additional information please let me know.