nope ...... un-attributable second half C20 decanters exist in their thousands - so in the absence of a backstamp etc., almost impossible to run down a maker.
about the only thing you might say is that it is of better quality if it has matching nos. than otherwise - just fill it with a single malt, and use it - alternatively give it to someone else in the family as a present, and say it's an antique that cost an arm and a leg - hopefully they'll never know the truth.
