This site is rife with abbreviations. Some I have figured out, some not. I got a link to Coin Collecting Terms and Abbreviations, but they have nothing on "RPM", "VAM", "PL", "CAC". It would be "PDG" if maybe there was a listing on this site. Or if there is, where?
RPM = Repunched mint mark VAM = A variety coin (Morgan & Peace Dollars) identified by the authors Leroy Van Allen and George Mallis. PL = Prooflike CAC = Certified Acceptance Corporation which is a company that verifies the TPG grade as solid for the grade.
What we use are actually acronyms, not abbreviations. I believe there are several threads here concerning them which detail them all in one place rather than looking them up individually. Use the search feature here using the word acronym.
Searching for "[Abbreviation] coin meaning" (without the quotes) in Google helps a lot. RPM = Repunched Mint Mark VAM = Van Allen-Mallis PL = Prooflike The others I don't know but you can try using my Google tip Edit: @tommyc03 is right, it should be "acronyms".
Here's a start, pretty sure there is a more recent one, I'll let the mavens handle that: https://www.cointalk.com/threads/exhibit-the-blog-part-2-of-2.112986/
Thanks for the help. I guess my misstep was searching for "abbreviations" rather than "acronyms". I actually did a Google search on it, and from several sources came away with this > An "initialism" is a series of initial letters of words in a phrase that form an abbreviation but aren't pronounced as a word, so I guess most of our terms, such as "BU" and "FBL", are technically initialisms. An "acronym" is an initialism that is typically pronounced as a word, such as "POTUS" or "Scuba". An "abbreviation" is a shortened version of a word or phrase, such as "circ" or "DCAM". Plus we have the beloved "slang", like "Frankie" and "Wheatie". But since "initialism" isn't in general use, we'll go with "acronym". OBSLN - Old But Still Learning Numismatist .