No, it's definitely not Chance, but as to who made it is anyone's guess. You have a choice of three main European makers (although I acknowledge there are almost certainly many more smaller ones):
VEB Obernau (East Germany
Spiegelunion Flabeg (West Germany)
Flamingo Halfweg ("Benelux", although most likely Dutch)
Within the UK there is Webb Crystal, based in London. I have found out that the company was still fabricating slumped glass into the 1970s. You then have distributors: Jones & Co, Astra, etc.
Sadly, until catalogues or company records become available it will be very difficult to assign any maker to these unknown plates.