I didn't say "all" did I? I sure hope I didn't 
*too lazy to check*.

When i bought my first and only VHD cel from 
Anime Link at AX 2002, it, as well as many other 
that I saw, were stamped. I think i mentioned 
this to Heather, and I remember hearing that they 
had just started stamping them because of the 
whole "stolen sequences" controversy.

Of course, my memory could fail me on this. 

But the stamp itself is probably about an inch in 
width, and is a clever rendering of an "a" and 
an "l". It was in the upper right corner of the 
cel. It really didn't bother me that much. And I 
don't know if they put it on ALL of their cels. 
You'd probably have to contact them for that 
information, or to clarify anything you hear from 
other people (a.k.a. ... me)