Try looking at some of the BBC (and maybe C4/UTV) websites for programs like Flog It, Antiques Roadshow, Cash in your Attic etc. - they may have details of prices things have sold for or valuations given which could give you an idea of what to expect (bearing in mind that would be in the UK). Or see if anyone else is selling something similar on Ebay. My dad used to have an antiques guide, think it was called Miller and is republished every year or so - you could check your library for a copy of a recent one also.