I think I've seen more detailed information. That seems to indicate only 12 print runs, though it looks like I have a copy from the 13th print run (I wonder if they skipped a print run number or something?).
Thanks for the info ffilz. 12 or 13 seems a safe bet at this point. My personal copy is a 3rd print.
In my copy, the row of print run numbers definitely starts with 13, but the article implies the print run data is taken directly from GDW records. I may just be remembering this article, but I thought I saw an article with the numbers for each individual print run, but I can't find that now.