not so sure - those seats have been recovered with new Alpina fabric and new foam - they are too puffy to be original and the fabric isn't faded / discolored. when they sourced the new fabric they probably sourced the horizontal badge.
The ad should say, the car identifies as an Alpina perhaps.The ad is clear- it says that this car has an Alpina head. There is no picture of any of the three stampings required to show that this is an actual B2 engine either as a head or a block.
I think the seller should get down there with a boroscope and take some pictures if he wants top Alpina B2 money.
Apart from the photos included in vintage test reports in AutoMotorSport or Sport Auto, I know of no "official" image of an E9 Alpina.
At the time, Alpina was more a racing car tuner and an accessory manufacturer selling special parts.
In their catalog, you won't find 16" rims or seats with the fabric that would later be used on E21s. It seems to me that the seller of the car offered by Légendary Motorcar does not claim that the Alpina preparation was made at the time. The title of the ad is ambiguous, as is the case with everything that passes through the hands of a marketing agent.
A part les photos incluses dans les comptes rendus d'essais d'époque dans AutoMotorSport ou Sport Auto je ne connais pas d'image "officiel" d'une E9 Alpina.
Alpina est a l'époque plutôt un préparateur d'auto de course et un accessoiriste vendeur de pièces spéciale.
Dans leur catalogue on ne trouve pas de jantes en 16" ni de siège avec le tissus qui sera plus tard utilisé sur les E21.
Il me semble que le vendeur de l'auto proposée par Légendary Motorcar ne prétends pas que la préparation Alpina a été faite à l'époque.
Le titre de l'annonce est ambiguë comme pour tous ce qui est passé entre les mains d'un agent marketing .