I believe you might have it correct. I have "read" where some of those were 69 and some were all the way into 72. I have a 72 bass adorned with one of those. Who really knows for sure?! Ludwig was the backlot bunkhouse of OZ in the 60's and 70's.

I bought one of those snares back in 1980 from the Long Island Drum Center. I believed it to be new and paid $150.00 (chrome over steel). I sold it earlier this year for over $400.00, on ebay. However, my drum had a serial number. It was in as good condition as your picture and it was a great "cutting" drum. Enjoy!