I think I got the rest of the inscription figured out. It is a dedication to Marcus Aurelius. But what does the last abbreviation, D.D.P., stand for?
The inscription is from a statue base in Caserma dei Vigili in Ostia Antica.
According to Sandys's Latin Epigraphy: An Introduction to the Study of Latin Inscriptions, "D.D.P." stands for:
decreto decurionum publice
The last "P" is sometimes replaced with "P.P." or "PEC PUB": pecunia publica.
A decurio was a public official who, among other things, collected local taxes and was responsible for certain public works.
This is essentially the Latin equivalent of, "Your local tax dollars at work!"