MicrostockGroup

Interesting question. I don't know how the agencies do it, but here is one way.

-Open Notepad (or other plain text editor)
-Drag the .eps file into it.
-If it is an eps 8 file, you will see a line like this in the top few lines of the file (probably the second line):
%%Creator: Adobe Illustrator(R) 8.0
-If it is an eps 10 file you will see a line something like this (maybe the third line):
%%Creator: Adobe Illustrator(R) 13.0

AI files are more complicated.
Maybe other people know of better ways to do this.

@Noodles
I tried the action thing but for the Save As... command remembers the whole path and filename, and it doesn's save the EPS save dialog parameters. Too bad, this is the most important thing I want...
I'm checking the open paths inside the "Document Info" panel, bitmaps at the "Links" panel... Is there an one-click solution or this is the way?

@michaeldb
Viewing works fine with Total Cmd... It seems to me that %%Creator: Adobe Illustrator(R) 8.0 is written only for the v8, above v8 the actual version is written. So I guess you have CS3, this is why you posted %%Creator: Adobe Illustrator(R) 13.0. I analyzed an EPS coming from CS5, there is %%Creator: Adobe Illustrator(R) 15.0. This EPS is supposed to be V10-compatible.

You are right, I do have CS3. You know more about this than I do. It is an interesting subject. As you said, agencies have software to read the files and determine what version the file is compatible with. I wonder what that software is and where they get it. If you find out, please let me know.