Brad, you won't get much of a bevel on a plate that thin. But here's a way to do it.
I assume it is not inlet into the wood. Black the edge with felt pen. Now scribe a line around the outside using either a Vernier's calipers or a pair of dividers. Now scribe a line parallel to the edge however wide you want the bevel to be. Mount the plate on a piece of wood that you can set in your vise. Use Bondo, hot glue, or what-have-you. Cut away the wood to allow you access to the edge without having to deal with it when you're filing the brass. Now file away the brass between the two lines with flat, triangular, and round files. Use the same files to back your abrasives for polishing, and there's no fussy complex curves that can elude you. It's easier with brass that is 1/8" thick to start.
