Keinath Automobilbau built 300-350 Ascona-convertibles, which where sold for 39950 to 42000 DM.

The opel-dealer "Häusler" in Munich sold the other version of the convertible. The price for the changement into a convertible was about 12.600 DM. It could be ordered at every opel-dealer. You simply ordered an ascona and as an extra (Nr. 74-7) the option "convertible". After 4 weeks you did get the car.
The plans therefore where made in England, by the "Planungs- und Konstruktionsbüro International Automobil Design" (IAD).
The realisation of their plans was managed by an english-german cooperation, the engineering-office "Hammond & Thiede", with settlements in Dover and Sulzbach am Main (Germany).
After several subenterprises (e.g. Michelotti in Italy and Tropic in Crailsheim (Germany)) failed, the carossier "Voll" (in Würzburg-Heidingsfeld) actually produced the convertible under the trade-mark "Hammond & Thiede". (In their adress in the prospects you can see them firming as "Hammond und Thiede" but their telex-adress in the prospects was: 68879 voll d.)
(Voll also built special cars for arabian oil-sheiks and "jeeps" for the german police. They also built the cabins for the legendary truck "Opel Blitz".)
Between 1984 and 1988 they built about 3000 ascona-convertibles. ("Deutsche Cabriolets seit 1945", Author: Hans W. Mayer/Joachim Kuch, Motorbuch Verlag)