I tend to agree with Kevin, Remember that the Pagodas were imported to the US first by Mr. Hoffman of NYC, and was placed in Stuedebaker showrooms, from this beginning, MBNA emerged and became the sole importer of MBs in America (only one other importer since then, importing the G wagon for a time). This was not a company in the Daimler-Benz Corporate chain. Also at that time, almost all MBs ordered to be imported were automatics (very some exceptions to this on special orders). It was unheard of in the US to see a stick shift MB, SL included. With this in mind, there was no need to display to the driving public that this car was an automatic, the American public expected it was. Thus, there was no need for the "Automatic" nameplate. European Mercedes, on the other hand, automatics were an optioned item and carried the nameplate to show the additional option thru all models. During the 80s, when "gray market" European models came to the US with stick shifts, therefore now you see many Euro Pagodas here in the US.
Also, yes, the nameplate for automatics was on the left side of trunk led, under the 230-250-280SL nameplate. See Laurence Meredith's book "Original Mercedes SL". I think any of the Pagodas that show automatic on the right side of trunk led were placed there for symmetrical reasons only. It is possible that original owners had dealerships put the added nameplate on for what ever reasons.
Bob