Hello! I may be interested in purchasing a Hitler photo postcard from an online dealer. The postcard is unmailed and unmarked. All it says on the reverse is AGFA. Would this be considered a "real photo postcard" or a mass-produced copy? Thanks!

I would bet it is a mass produced example. Here is a small selection I found on line in about 10 seconds. 

I Googled the photo to see if it was possibly mass produced and I did not see one. I have a feeling it is a real photo on Agfa card stock.

An original snap shot is worth more.

To tell if it is a real photograph you will  have to look at it with a loupe. If the picture is made up of tiny dots (or sometimes dashes) it is what is known as a half tone and was printed on a printing press. These were produced by the thousands and are the most common. If there are no dots and has shades of gray it is what is known as a continuous tone and is a photograph. This does not mean it is a one off only that it was harder to make and more expensive. If the back is printed as a postcard then there are many more of them out there, better than a half tone but still quite common. If the back is blank and on card stock then it is probably a souvenir given out or sold at rallies or parades, better than a post card but still common. If it is a photograph on photographic paper then you have a very limited run or maybe even a one off, the trick is to find unpublished pictures.