The best advice that I can give you would be to always buy from a trusted source, particularly if you are buying online. The listings on the well known online auction sites contain huge numbers of modern fakes being passed off as the genuine article. Beware of descriptions such as 'Found in a car boot sale', 'Found in a tin in my loft', 'Left me by my Grandad' and even 'from an old European collection' because the picture of the item next to the description may be of something that was made very recently and worth nothing at all. The online auctioneers do not seem to want to do anything about this, and they still get their commission so maybe it is not important to them.
Pictured is part of a 'genuine' old collection that I purchased from a reputable auction house and that I am currently listing. Any reputable dealer will guarantee the authenticity of what they sell for the lifetime of the purchase, but if you see something online that looks like a bargain, beware!