Ivo, I first encountered this load in about 2000 loaded in a copperwashed steel case headstamped 10 9x19 99. Subsequently, I obtained a load with a KOPP headstamp like the one you illustrated. I was told they were self defense loads but I know nothing of the internal construction of the bullet. I was surprised to see the Kopp headstamp on this Bulgarian load. The Kopp marked cases seemed to be Tula (TCW) production for a Czech company. At least the Kopp boxes seem to to all be marked with a Czech address. Do you think the cartridge you illustrate was loaded in the Czech Republic for someone in Bulgaria or the Kopp cases were simply used by Someone in Bulgaria. My ball cartridges with the same headstamp, which came from the Czech Republic, have the same red primer.
Interesting cartridge, thanks for posting it.