Abbreviations can be a bit puzzling. Take A.D. for instance. The usual meaning is Anno Domini which is Latin for "the year of our Lord". If Christ was born in AD1 then the years before Christ was born would be labeled 1BC and so on. This system of numbering years was invented by Dionysius Exigus in AD 525 and is widely used in Julian and Gregorian calenders to this day. Could the A.D. at this location stand for Anno Domini? Other options could be Architectural Digest, Authorized Dealer or Academic Department, just to name a few. One could probably come up with a few of their own. However, I'll just say that this cache is established in A.D. 2019 and is available before, during or After Dinner. Watch for muggles especially After Dinner.