Try and get ahold of an AMG catalog, either from AMG West, or one of the German ones from www.ebay.de if you need one to see a good picture of them. I have tyhe original US AMG price list from 1988 and the spoiler you are talking about for the W123 is AMG part # 7088011, retail $245, dealer price $196 That is from the Westmont Illinois facility that is not in business, (parts bought out probably by Beverly Hills Motoring Accessories, AMG West and who knows else? - AMG West still in business in Richmond Calif., might be worth a call, not on the net)

It would be pretty hard, but not impossible, to get a an OEM AMG spoiler, but nice if you could find one

The rear OEM AMG spoiler would be painted in the body color of the car, it is part of the kit

I saw a Euro version W123 280CE coupe (Euro bumpers and lights, euro wind deflector, velour seats) that had a black rubber ducktail spoiler, bodey color was yellow though, it didn't look too bad, that wasw in SF a couple of years ago, guy lived in my neighborhood then

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1991 560 SEC AMG, 199k <---- 300 hp 10:1 ECE euro HV ...

1995 E 420, 170k "The Red Plum" (sold)

2015 BMW 535i xdrive awd Stage 1 DINAN, 6k, <----364 hp

1967 Mercury Cougar, 49k

2013 Jaguar XF, 20k <----340 hp Supercharged, All Wheel Drive (sold)