1999 Mercedes-Benz SL 55 AMG Mille Miglia the rarest SL R129 

No. This edition of the SL 55 R129 is more rare. Only ten. SL 70had 150 pieces, SL 72 35 pieces and SL 73 had 42 pieces. The normal SL 55 without Mille Miglia had 55 pieces. But there was a SL 36 for a tennis cup in Stuttgart, they built only two of them.

SL 55 AMG Mille Miglia Storica - 12 units produced SL 73 AMG - produced approx. 85 units

i do believe so, AMG made less than 1000 cars in the R129 variant. i'm a member of the UK MB owners club and i took some notes while i attended a talk on the R129. Below is what i wrote down from that talk (the talk was back in 2015 and i cannot be 100% sure i wrote the figures down accurately). nonetheless this is what i noted: # SL 60 AMG - About 600 to maybe 633 units (this includes the 1991 500 SL's that AMG took from MB and modified and rebadged as the 500SL 6.0 which have the VIN's starting WDB129066******* which have the 6.0 litre 32 valve V8 engines. Note AMG were independent until 1993) # SL 72 AMG - 35 units (on sale in 1995 but production stopped and resumed in 1997/8 as the SL 73 AMG) # SL 73 AMG - 50 units (on sale in 1997/8 till 2001) # SL 70 AMG - 150 units # SL 55 AMG - 65 units # SL 55 AMG Millie Miglia - 10 units The SL 55 AMG is the predecessor to the production R230 SL 55 AMG (however the R129 has a normally aspirated engine whereas in the R230 they supercharged it). hope it helps 👍