I don't know of any use of APB in coins or grading. ABP is occasionally used and it stands for Average Buy Price, or what a dealer would on average give for your coin.
it means that a porfecinal has authenticated and determaned the codition of a coin
PR is a grading system used for proof coins
The most expeditious way to get a coin graded is to locate a coin shop nearby - present the coin to the owner for grading. If he/she is uncomfortable to do so, he/she will refer you to a numismatist (experienced coin collector).
DCAM stands for Deep Cameo and is reserved for proof coins
Proof Grade 69 Deep Cameo finish