The first alpha-character is the last to advance, the second alpha-character, is next to the last.The progression appears to be 0AA0, 0AA1, then after 9AA9 would come 0AB0, etc.
Applications for an antique tag received after 1/31/05 get the new style plate, or a purple plate holder can replace that plate for $7.50 and a completed MV-44.
All new plates will be in the A00A format - no reissues will be done of existing numbers. Note that the characters placement is not always uniform. Also plate series P00A - P99Z is reserved for Person with Disability Motorcycle plates and would not be duplicated.
This also shows two plates with the same number issued many years apart. FAKES: These plates have a number from the Classic Car series, on what appears to be a '77 base, but without sticker wells, using a pre-1971 font, and were seen at a car show.
There are also reports of new plates X5 and G8 being newly issued. They are not believed to have been issued by Penn DOT.
Close examination of sleeves and collars can provide valuable information.
Other things to look for on women are the presence and size of a bustle and the fullness of the skirt.
Another extensive online resource is the Library of Congress.
Enter a photo type into its search engine and you will see many examples that may turn out to be similar to the photograph you are researching. Both the men in my photo are young, but one appears to be older than the other, and he has arm slung around his younger brother's shoulders. The elder is wearing a watch chain and a pinky ring. Michael was seven years older than Peter, who was seven years older than Timothy.
The elder man is wearing a collarless shirt — too bad, because it's easier to date men's collars and neckties.