Identifying the image type within a PDF file?

Is there any quick and easy way to determine the basic or current 
structure of an image of unknown original vintage that is embedded in a 
PDF file, without trying to extract the image, or edit the whole PDF? -- 
for example, by searching for specific strings inside the PDF file with 
a text editor, or by examining some metadata associated with the file 
using Acrobat?

I have a large number of single-page PDF files (single slides) which 
mostly consist of a single image or graphic, plus maybe a small amount 
of added text or text labels.  

I'm sure the images are sometimes pixel purely in character (JPEG, TIFF, 
etc); sometimes fully vector in character (EPS, Illustrator, or vector 
PNG); sometimes "mixed"  (i.e., they were acquired in a potentially 
vector format like PostScript, EPS, PNG or PICT, but may have primarily 
a pixel image inside them); but I doubt very much anyone added any 
metadata about the original or the converted image character when the 
PDFs were created.

Any easy way to find this out?