Here are a couple links that may help in your information gathering:
https://pinside.com/pinball/forum/topic/what-are-the-differences-between-mm-and-mmr
https://pinside.com/pinball/forum/topic/nib-mmr-vs-average-original-mm
https://pinside.com/pinball/forum/topic/mm-vs-mmr-on-which-side-do-the-pinside-faithful-line-up