The ones on eBay are original version all-metal, probably very early to mid-'60's era, recognizable by the full 360° wraparound solid housing with no separate slotted base. These were available with both flat and convex mirrors. Later on, Moss added chrome plated over conductive primed plastic (see photo of example of broken tail with white plastic core visible). The plastic ones are generally recognized by a housing that has an open slot on the bottom (also seen in first picture) that slides into a raised black plastic base. The base incorporates the spring loaded adjustable mirror, and uses a long screw seen on the mirror side of the black base that extends to a metal threaded socket in the tail of the detachable chrome cover. BTW, this long screw does rust, making removal of the housing impossible without serious damage.
The old style all metal ones were typically bolted directly to the car as one piece without any added base, while the plastic ones were all two-piece with slightly raised black base/mirror assembly that mounted first, then chrome plastic housing cover slides on, and is secured with the long screw. I’ve never seen any of the all metal units on any Europas, but it could be someone replaced theirs for whatever reason, maybe damage, back when you could still find metal ones and the few transitional metal ones on various wrecked race cars.
If you have the black plastic base with visible small screw head and a gap in the chrome on the bottom of the housing, tap on it, and if its a hollow dull thud, it is chrome plated plastic, not metal. But there is another very simple way to verify whether you have metal or plastic. If they have “Mach 1” under “Sebring” on the housing, they are chromed plastic. The original metal ones were only marked “Sebring” without “Mach 1” like the metal ones on eBay, except for a few during transitional metal to plastic that were a sort of hybrid, and had both words on a single line, not one over the other. Or you could remove the chrome shells via that small front screw head, and you will know they are way to lite to be metal at less than 3 ozs. each. But if the screw won't budge, it probably has rusted to the metal socket in the nose, so don't push you luck if it doesn't want to turn.
The much newer Vitaloni and other knock-offs are even easier to spot. All have a somewhat larger front housing section than any original Sebrings, with a thick roll-over lip around a larger convex mirror. They are also available in solid black. Although construction with the slotted base is essentially the same, an original housing will not swap onto the Vitaloni base. The older ones use a long fine threaded machine screw into a metal nut receiver secured inside the nose of the chromed plastic housing, while the new Vitalonis ones use a longer coarse-threaded screw directly into a short plastic molded tube in the housing nose -- which can strip fairly easy if you over-tighten. Otherwise, these new copies are easy to find and cheaper if not quite as sturdy, but they do have one other benefit: a wider panorama using a larger and convex mirror rather than a smaller flat one.
I think this seller could eventually get a very serious price - maybe not quite this much, but who knows? And having original box and papers as further proof of pristine condition will add more. The supply of both the metal and original plastic ones in new condition is only shrinking. I have two pairs of original plastic “Mach 1” versions I may put up on eBay at some point (see pictures), but updated with stainless steel long screws that can’t rust. For someone sitting on a £3-10M+ car that came OEM with either ultra rare all metal mirrors or later rare plastic, what's a few extra 100 quid for 100% correct pristine or NOS part where anything non-original only devalues the vehicle? Both Sebring versions were factory and/or US DOT compliant import originals for a number of vintage Ferrari, Lamborghini, Maserati, Bizarrini, and more than a few vintage race cars -- not exactly a short list of potentially serious buyers for genuine NOS or close to it, willing to pay a premium for maintain authenticity.
