As he is speaking about the Praktiflex, having no flash synchronisation. I got the 3. generation Praktiflex, the FX from 1952. It by then got internal flash synchronisation. Both X and M. Although the PC connector already had been introduced, it still got single-pole jacks, thus 3 in a row.
First Praktiflex/Praktika model to have flash synchronisation was in 1951, but jacks came on a accessory board. Weird and dangerous.