Agree initials are a possibility. But it might be “Rich Girl Princess”? “Rich Great Princess”? “Rich Gorgeous Princess”?
But my fave theory is Urban Dictionary: RGP.
Our Mercedes owner only has RGPs. And boy, is she spoiled about how she solves them. And even moreso, she’s proud of that. Sorta like Paris Hilton or a Kardashian woman is her role model.
M’kay is a common jokey spelling for Okay. Which carries a lot of different connotations depending on who’s using it: Urban Dictionary: mkay. Used more by women than men IME/IMO. So perhaps it’s MH M’kay meaning something like “My initials are MH and if you’re not OK with that, stuff it.”
Or it could just be e.g. Michael Herbert McKay or Mary Helen McKay.
I scored a couple yesterday but it was a bad day for notetaking. The only one I remember was a scruffy car festooned with anti-trump commentary whose plate was KATALST. I hope they can catalyse something to end this era of madness; we could sure use it.