550-15 was the last prototype 550 built by Porsche, completed on 12th March 1955, after the first production customer cars had already been delivered from the Wendler factory. It used quad cam engine #547-12 from 550-14, with a Weinsberg/Porsche body likely sourced from a spare Le Mans Werks shell, retaining the high fins, side gills and external oil filler, but incorporating the new slanted headlights from the customer cars.

Sold new to Wolfgang Seidel, registered in Frankfurt, the car was raced across Europe and the UK from April 1955 to August 1956, regularly finishing on the podium. Notable results included the 1955 Mille Miglia (car #541, co-driven with Helm Glöckler), finishing 8th overall and first in the 1500cc class. By mid-1955, the original finned rear clamshell was replaced with a Wendler unit featuring rounded fenders and round tail lights, without the side gills.

Chassis #550-15 has a documented race and ownership history that has been researched and verified through primary sources. Accurate provenance information for this car is available upon enquiry through the contact page.