I have connected the D-126 distiller number with the following brands: Calvert, Seagrams, Wolfschmidt Vodka, Four Roses and that is about all I can tell you.
The key to tracking down such 20th century items is finding a labeled example. Your particular decanters or bottles seem to be fairly scarce. I found only two examples with a lot of searching.
You might also browse eBay or general searches for advertisements for these brands from the 60s and 70s. Maybe you will find a match. I have found that during this period, the fancy decanters that were used by brands are pictured frequently in their ads....
