"Fanfare Zweiklang" code 452 was available for most MBs of that era, but probably not necessarily ordered for the W113 since they had the "Starktonhorn", loud horn, as standard equipment in comparison to the weaker horns of the lesser models. Also, the other models, like e.g. the W114/115 sported these optional horns outside in front, above the bumper,chromed and visible and as such had some appeal for certain people (I once had a 114 with them and the disadvantage was that when you had a minor frontal collision they were pushed back into the sheet metal, resulting in additional unnecessary damage). On the W113 they would have been under the hood, and less loud than the standard horns.
Klaus
1969 280 SL