Mystery Plates

(Click on pictures to see larger version)

From Eric Tanner

From unknown

From eBay (buch1259) via Charles Metz

According to information received from Eric Tanner, Pennsylvania passed Act 160, the Outdoor Advertising Control Act, on December 15, 1971, effective immediately. In Section 7, the law states: "An annual permit shall be required for each outdoor advertising device...A tag indicating that a permit has been duly issued shall be affixed to the device or structure by the department."

The billboards affected were those within 660 feet of most federal and state highways, with certain exceptions. PennDOT administered the program, which was a result of Congress passing the Highway Beautification Act in 1965, appropriating money to states which complied. (It was "Lady Bird" Johnson's initiative!)

Eric suggests that the "ADP" tag stands for Advertising Device Permit, and that it was issued in 1972 or possibly 1973. He does not know for how long they were issued, or why they aren't much more common.

Size is 4.5" x 8", same as motorcycle plates of the era.
Bicentennial Plate Mystery
From Charlie Metz

The color scheme of the plate is opposite of a typical Bicentennial plate.
Diplomat Plate (?)
From John Anshant

From information received from Ned Flynn, there was a wealthy family in the Stroudsburg area some years ago that had an affinity for New York City theatre. They purchased vanity tags with DPL in an effort to appear as diplomats hoping they might receive favorable parking, It is unknown how the use of the keystone separator and a dash came about.
Flagship Niagara Mystery
From Mike Barns

Note the absence of the EXP. 6/96 which is normal on the plates that were made available as souvenirs after the discontinuation of the Flagship Niagara plate. At the time when these plates were issued, this was a pet project of Governor Ridge (being from the Erie area). This plate could very well have been given to him.
Sample Mystery
From Bruce Bufalini

From Bruce Bufalini: "Picture taken September 22, 2001, at the University of Pittsburgh, Greensburg campus. The plate was on the front of a DEP (Dept. of Environmental Protection)-owned car. There was some sort of conference there held by the DEP, and at the time I had theorized that there was a DEP prefix plate series reserved for them, though I've never seen another such plate, sample or real issue, before or since.