Success!

I first tried the apt-cache policy command exactly as suggested by Telemachos (that apparently worked fine for farslayer), and it said that it couldn't find the package. I then ran apt-cache search linux-image, and from the list I was able to determine which generic package name I should have (and I learned something: the -686 is the compilation for my processor). I typed that in manually (apt-cache policy linux-image-2.6.18-6-686), and the output I got was exactly what farslayer showed.

So I am running the correct kernel. I'm still confused about the datestamp, but I don't think there's any way to know the answer there.

Thanks everybody!