Are you selling as an auction? I always start my jewellery as an auction. Personally I don't think it is any older than 1980s - MOP can be dyed any colour. Bear in mind many of those prices are what is being asked. If it was mine I would start at $25, but as you have to build in your fees, perhaps $35. It is an attractive design. I would not "freshen" the brass - many buyers prefer the oxidised metal look. Good luck.