Haehn was a large Alfa dealer in Mannheim/Germany and one of the more prolific GTA shops in Germany from early on winning many Group 2 events particularly in the southwest of Germany. Tests of his race GTA's in Group 2 trim were featured in the automotive magazine "Auto, Motor und Sport" in the late 60's. As pointed out above, many well known drivers that include Jochen Mass, Gerhard Schueler, Bern Fischer and many others that were in one or another way involved with Haehn.
The early career of the car in the pictures above was in Group 2 with Gerhard Schueler. Schueler had a bad accident at Monza with a GTA-SA and later owned the discotheque Dorian Gray at Frankfurt airport, as well as a restaurant on top of the Frankfurt TV tower (Europa Turm).
The later carrer of the car was in Group 4/5 - GT and Special GT. At this point it was highly modified, mostly with aid from the expertise from its driver Bernd Fischer who continues to own a CNC machine shop that is involved in providing parts for Formula 1, DTM, aerospace and medical industry.
Fischer CNC-Technik GmbH
A detailed history of 613124 participation in various events is in the second edition of Alleggerita.
The last time I saw 613124 being used in anger was when it was driven by Helmut Haehn at a historic event at the Nurburgring sometime in the late 80's. A picture of it in that configuration with a 1300 4-valve engine is in the first edition of Alleggerita.
The picture shown in this thread must be fairly recent, as in that location in Haehn's shop there used to be a lot more cars, GTA's, GTA juniors and GTAm, at times being store one on top of another. Haehn sold the cars off over the years. To my knowledge 613124 was one of the last ones to go.
The MA-BF 555 license plate shown on the car was typical for Haehn where the second set of letters usually reflected the initials of the driver, eg BF for Bernd Fischer.