A couple years ago a couple hundred Carl Zapletal (sometimes referred to as Karl Zapletal) glass plate negatives were unearthed in Vienna. Beyond that only a few original photos appear, though he must have made thousands of pictures - he was at all Austrian and most of the Hungarian races from the 1920s to the 2nd WW
When I looked out of the tram window these days I discovered the still existing Zapletal shop sign in Vienna. Nowadays the facilities are used by a restaurant.