Even though the blade is missing, the hilt is so nice, with the guard having that typical shape. Amazing how consistent these swords are in having that little bump detail on the guard, that mid-swelling in the handle. The contraction for the lower two fingers, which falcatas also poses, yet Italic/Etruscan examples seem to lack.

How would you characterize a Macedonia type vs. a Greek type? What are their distinguishing features?

Although on this one the blade is almost straight, the handle is much more canted/curved. So the effect should probably the same. I'm guessing the blade tip is missing. Otherwise, I'm getting "parang' vibes coming from it :)
I think you should post it. The larger the sample size, the better. This one from the Musée d'Art Classique de Mougins in France had me scratching my head, so I hesitated to post it. Its proportions seem strange. Any thoughts?
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Source: http://myarmoury.com/talk/viewtopic.39375.html

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I managed to find a better view. A photo by Michel Allal on Google.

I think those two blades might look like xiphos blades because they're more straight than other examples, but they do still have a slight curve, and appear to have more weight towards the end of the blade, both of which factors would contribute to it having the moment of inertia of an axe. They also likely both are single edged (except for maybe the top third of the blade, like Parnell describes), in contrast to a xiphos.

There does seem to be a grey area, but instead of classifying one as a kopis by the asymmetrical handle base I would still say the blade is more the defining feature. I like Tarassuk & Blair's classification, for example: a makhaira is generally a single-edged blade, and a kopis is a subvariant that is curved and meant to "cut" or "chop" as implied by its definition in ancient Greek. I have a hard time imaging that the Thracian example in that Bulgarian museum would be described as a kopis despite its characteristic handle just because it looks made more for thrusting than slashing. Although even that is an assumption because maybe it also is single-edged and has a moment of inertia similar to a short axe — it's hard to tell from the pictures.

Essentially, I think how they would have used the blades dictates what they would have called them, and it's not any one of these characteristics that would have defined a kopis, but some set of all of them; the asymmetrical handle helps keep the sword in hand when slashing, and the single-edged, forward curving blade with the moment of inertia of an axe helps deliver a slashing blow. For all we know, the asymmetrical handle might have been slapped onto the blade of a xiphos because it was comfortable, or a status symbol, or the hallmark of a contemporary craftsman/workshop — and maybe that's what the Thracian example from Bulgaria is.

Another key characteristic I've noticed on these types is the notch in the handle right before the blade, easily seen on this example. All of these consistent features are factors in how I personally classify the "Macedonian" type: the bird head, usually with gems as eyes, the tapering shape of the handle as you described, the solid iron grip, the guard with the characteristic bump, the notch before the blade, a long blade with a slight curve and wider end, and a ridge originating from the notch on the handle but continuing out further from the flat edge of the blade the further from the handle it gets. And I guess a sharpened edge on the last third of the back of the blade is also characteristic, though it's harder to tell from just the pictures how many of these have that.

Maybe calling it "Macedonian" is misleading, despite most examples apparently coming from Macedonian sites or graves. I mentioned my theory above of all of these characteristics being a hallmark of a contemporary craftsman/workshop, and I think the King Seuthes III example gives some credibility to it — it shares many of these characteristics (the blade looks different but it was heavily reconstructed), and King Seuthes III was a king of Thrace while it was subjugated by Macedonia, and soon after Alexander the Great died he rebelled against the Macedonians. So at some point maybe these swords were being commissioned by opposing armies?

Here's the makhaira example I was talking about, and another "Thracian" kopis, both of which fall outside my "Macedonian" classification but still share enough characteristics that make me want to describe them as Greek. They share some characteristics with this example I posted above, mainly the handle with rivets that would have secured an organic material, and the horse head. Both of these are from private collections, so the data isn't very reliable, but it's interesting that the "makhaira" on the left is completely straight and even longer than the typical Macedonian kopis (which probably would have been used by the Macedonian companion cavalry) — I wonder if it has a single edge or not. The other example comes from the Vassil Bojkov collection, and it's hard to tell how much of it is original, if any. I think we can reliably say the wood was a recent restoration, and I suspect the blade might be modern too. Maybe it is just the iron handle that is original?

What's interesting though is that this example you posted has a similarly-wide/thick guard to these two examples. The typical Macedonian examples have much more pointy guards. What do you think?

I found a high resolution photo of the Vasil Bozhkov Museum (Васил Божков) makhaira. It says "makhaira sword of the 4th century BC, with a unique hilt with an exquisite hilt representing the figure of a galloping horse with a copper-inlaid bridle".
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Mahaira from Zlatinitsa - Malomirovo
More info about the Bulgarian finds here
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Plus a few more, regarding which I have no further info.
https://commons.wikimedia.org/wiki/File:Kabile_001.jpg

This is not necesarily related to kopises.
If you like ancient objects, but don't have the budget to travel around, then this flickr account might interest you.
Enjoy! https://www.flickr.com/photos/dandiffendale/

This one is very nice as well
https://www.flickr.com/photos/prof_r.../albums/page10