I was very surprised when I saw that there is actually video footage of the early Heck cattle - particularly interesting: it shows a herd of Lutz Heck's diminished cattle, which where introduced and kept like red deer in the Rominter Heide in former East Prussia, today Russia and Poland. It must be from the 1940s because the cattle didn't arrive there prior to to 1940.
To a very large extent, those cattle are a combination of Lidia, Corsican and Camargue. They actually look like just another southern-european medium-aurochs like breed. They were very small as well, among other deficient aspects.