Check Opened file was created in PP 2003

[Sonic]

Hi,

I'm working with PowerPoint Object Library 12
and I need to check if a file with a "ppt" suffix was created in PP 2003.
The "ppt" itself is not enough to know what I need,
because it is possible that the file was created in PP 2007 and saved as PP
2003 with a PPT suffix.

Thanks,
Sonic