[Pharo-project] detect if image was saved with Cog

Hi guys Is there a way to find out (from outside of the image), if an image has been saved with Cog? What I would like to do is something like this: $ head -20 myImage.image | grep <some expression> The use case for this is seaside hosting, where we only have squeak VMs to run images, so when an image is uploaded that was saved with Cog that image cause trouble. Any ideas? Cheers, Max