@robpike this caught my interest and went to search David Hagelbarger and see that they dont have a wikipedia page wich seems like quite a shame. I dont see any references to their work on Nixie tubes either. So interesting how many people fall though the cracks of history like that.
@liaizon Here's some Hagelbarger for you.
https://www.researchgate.net/publication/348439425_On_Hagelbarger's_and_Shannon's_matching_pennies_playing_machines