They are the fastest stock engine in the beloved 123 body style engine that was ever sold in the USA, but their carbs were troublesome.
Back in 1980 I was looking everywhere for a used one and the only one I saw was a horribly filthy white one, which I did not buy.
They are very very rare in US spec form, as they did not sell many new ones here, but not that valuable.
Yours sounds like a really good one.
I would gladly pay $4,000 to $5,000+ cash for one that good, with just one owner, low miles, books and records from new, in a color that did not make me throw up (some W123 colors, like avocado green, DO !!!) and no rust or repaired body damage.
The W123 diesels outspld them by such a vast number, that I believe 1981 was the last model year of the 280e ever even sold in the USA, I believe, so I think a 1981, yours, very was very the last, though you could get a european gray market one into the USA or buy a new one outside the USA all the way to the end of the model run, which was 1985.
So to me personally, yours is a real find, and if I had the "means, motive, and opportunity", as they say, I would pay on the high side to find and own one like that.
Really beat down ones, 230e and 280e models, that years ago, failed inspection in West European countries, still ply the road daily in West Africa, Syria, Israel, Palestine, Iraq, Lebanon, Tunisia and Morocco, where they are cheap butmuch adored MERCEDES BENZ transportation.
(as seen for example, in present day Morocco)
Good readable and highly recommended book that offers a look into the process of exactly how it is done, getting one of them (in this case a beat up 190d W201 2.2 diesel) into the middle of darkest West Africa :
