When purchasing old and vintage cameras, one should try to avoid getting negative feedback by discussing the full story with the other party, even if it takes more than a dozen emails to rouse their interest and get a response - some sellers are very busy and quite likely make a living selling cameras and lenses and accessories on ebay.
Even if they have taken your money and are not responding, you should give them the maximum benefit of the doubt, rather than incur their displeasure, their invective, and their "libellous" remarks - give them another three or four emails, then ask PayPal to get your money back, rather than using the feedback tool as a means of rousing them and bringing their failings to light and the attention of the whole ebay community. After all, feedback is only really for POSITIVE FEEDBACK - it is only "noobs" who ever give negative feedback. And nobody gives neutral feedback with impunity, either.
Sellers who are Power Sellers are ebay favourites, so expect a phone call from ebay querying why you haven't paid for an item, even if you have been unable to as the item in question is under dispute, for example, or the Power Seller has failed to provide you with a correct invoice.
If you don't heed these words of advice when purchasing bargain cameras and camera parts and filters and the like, you will end up with comments on your account like on mine - and I wouldn't wish anybody to see them or experience remarks of their like !