The term "vintage" when applied to diving gear remains a very subjective concept. There's some consensus that the mid-1970s represent the dividing point between vintage and modern, but I expect there would be as many different answers to your question as there are people diving vintage.
I can't speak for regulators, as I'm into vintage snorkelling, not SCUBA, but my take on vintage fins is that they must be made from natural or neoprene rubber to qualify. Plastic-bladed fins with thermoplastic elastomer foot pockets don't qualify as vintage. As for masks, true vintage models come with rubber skirts, not silicone (yes, I do know that very expensive silicone-skirted masks existed before 1975 for the benefit of the few with allergies, but they're the exception, not the rule). For me, beavertails typify vintage wetsuits, while I always associate vintage drysuits with the wearing of "long johns" for warmth and unlined sheet rubber for watertightness.
Some, if not all, of these items of equipment are still manufactured nowadays, although you may have to find an online retailer in another country to complete the modern vintage/retro/classic ensemble. I prefer vintage snorkelling with new gear rather than somebody else's cast-offs, so I keep a look out for "new old stock" that has been in storage and never been sold, once picking up a late-1950s "Skooba Totes" vintage drysuit this way to complement replica suits of modern manufacture. There are more than seventy models of full-foot rubber fins still produced worldwide and there are still about a dozen blue rubber-skirted masks available around the world to complement the dozens of black rubber skirted versions still being made. I will tend to use such modern "retro" fins and masks when I snorkel nowadays, not least because they are easier to replace if a big wave carries them off, something that has happened to me on two separate occasions.
My advice is just to enjoy collecting and using old-style equipment rather than trying to define "vintage" too narrowly. Those items that can be dated pre-1975 can be regarded in some ways as historical artefacts, milestones in the history of our great sport. Some of us would prefer to linger at, and with, those milestones rather than accept uncritically the latest equipment which may be technologically advanced but may also be aesthetically unappealing to people who appreciate good classic designs more than the performance claims in magazine advertorials.
Oh, and I think AMF Voit had colored wetsuits out even before there were nylon-lined wet suits, if my memory serves me (which it might not on this matter).
