Further Suggestion überflüssig, schon drin.

"Ein paar" kommt dem umgangssprachlichen Register von "a couple of" näher als "some". Die Anmerkung "especially spoken" sollte aber auf jeden Fall dabei stehen!

"a couple of" bedeutet wie "ein paar" zwei oder eine kleinere Anzahl und man kann jetzt streiten, bis zu welcher konkreten Zahl. Darum geht es aber gar nicht. Wenn man es genau nimmt, gibt es in vielen, vielleicht sogar den meisten Fällen gar keine Alternative: "some" bzw. "einige" werden hauptsächlich als Attribut zu einem Substantiv verwendet und können nicht alleine stehen:

"How many drinks did you have?" "Just a couple." ("Just some" is not possible)
"Wie viele hast du denn getrunken" "Nur ein paar" ("Nur einige" geht nicht)

"A few" bzw. "einige wenige" würde zahlenmäßig "a couple of" / "ein paar" entsprechen, betont aber die Tatsache, dass die Menge gering war, und impliziert, dass man mehr erwartet hätte. Diesen Aspekt hat "a couple of"/"ein paar" nicht.

I would be interested in some native speakers' input too:

At school (in Austria) I learned that "a couple of" means "a small number of" (at least that's what I remember - it's been a few decades...)

When I lived in the U.S. (Michigan) I was repeatedly corrected that "a couple of" means "two" and that the only way its meaning differed from "two" was the fact that it did not mean "precisely two" (in the sense of "I believe: two", but *not* in the sense of "two or more").

Or, in other words:
"two" = "exactly two"
"a couple of" = "two" as in "two - as far as I know/remember - but I'm not sure"
"some", "a few" etc. = "two or more"

I wonder if this is a BE<-->AE difference or just a regional "difference in usage"

(Note: the above description is *my" abstract of the various explanations I got - they varied to some extent, but all had in common that "a couple of" does not per se mean "two or more" - but only "two")

I am really curious to get a more "global view" on this after all those years...

This topic has been discussed already more than a couple of times. Please confer
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Having thought about it a bit, I would say "a couple of" normally means "an imprecise quantity approximating two" and would therefore normally be used of something measurable in arbitrary units rather than something strictly countable. So "a couple of years" would mean a period of around 24 months (possibly between 18 and 32, for instance).

The object of being imprecise and the degree of imprecision may vary: "a couple of beers" may very well turn out to be between 1 and 6 pints.

"A couple of slices of ham", mentioned by Doris is a bit more complicated. The person serving in the shop will have to "convert" this imprecise amount into a countable number of slices and might wonder what the customer meant. OTOH "Could you fetch me a couple of slices of ham?" seems quite normal to me, the imprecision being intended to make the request more polite or less formal; "Could you fetch me two slices of ham?", because it is more precise, sounds more like an instruction or an order, with no imlpied discretion.

I agree with Mike E.

"A couple of" is used for countable objects and means "two, or possibly three, or conceivably even as many as four, if you're not counting carefully". If you asked someone for "two slices of ham" and they gave you three or four, you'd say "sorry, I only wanted two". However, if you asked someone for "a couple of slices of ham" and they gave you three or even four, you would not say "that's incorrect; I asked for a couple, not three [or four]"; you would rather say "thanks, but that's a little more than I need". "A couple" means "about two, but possibly more if they're small [like slices of ham]".

I would say that "a couple" does not mean "two, but I'm not quite certain", but rather "approximately two". For quantities, "a couple of" it means maybe 1.5 to 3, so "I haven't seen her for a couple of years" could mean maybe 18 to 36 months.

Some might disagree and say that "a couple" might include three, but never four.