I think the reason you have not gotten an answer is that there are differing opinions among the experts. I have even seen 2 opposite opinions coming from Sothebys!
For now, clean it but don't polish it yet. Bronze don't polish for any reason, but brass some say yes it was meant to be polished, some say no. Silver it raises the value to polish. Brass - jury still out.
Maybe more than you originally wanted, but hope this helps somewhat.
