I am a bit late to the thread, but wanted to respond to some of drumguy1988's questions.
I continue to gather information and will probably provide updated information in future versions of the Ludwig paper. I have already added more than 200 more reports of drums with both serial numbers and date stamps to what was available a year ago when the Ludwig paper printed. I have revised a dating guide for Gretsch drums twice already in the three years since it was first published.
I welcome any new reports of drums from anyone who wants to contribute. I am monitoring US eBay pretty closely, but if you see something somewhere else or want to report drums in your collection, please send them to me. I gather information on both Gretsch and Ludwig drums with serial numbers. More information is available in the back of my papers or at my website - www.GretschDrumDatingGuide.com.
Thanks for all of the interest and continued support
Rick