Try going to my website at gigconceptsinc.com and you will find a guide to 9mmP headstamps. It is old, from 2002 but covers what you are asking. Even better it is Free to download.
All three of these are pretty common rounds.
Hi Lew. Pm sent. Cheers
R-P is Remington-Peters, a common headstamp still in use.
dnh is a German WW2 code, being batch 2 of 1943 in this case. You’ll have to look up who dnh were.