Start with what the Horch 853 Voll & Ruhrbeck Sport Cabriolet is: a car with gasoline engine, from Horch. What it meant takes a little longer. 619 were built.
The engineering
The engine is gasoline engine. These are manufacturer figures carried by Wikipedia and Wikidata, not road-test measurements.
Where it sits
Its Horch stablemates include the Horch 10 and the Horch 670.