We can pretty acurately date Ludwig drums and Ludwig serial numbers are a big help, but not an exact science.
Other special features like badges, shell plys and the interior finish all help in giving you a date range of your drums manufacture.
Lugs, spurs, and 3-ply maple/poplar shell mold remained the same.
By 1975, the Ludwig Club Date outfit was no longer cataloged, and soon there after unavailable.
If you’re fortunate enough, your drum might even have a date stamp on the inside of its shell.
Here are some references you can use to date by serial number.
The web site link is available so feel free to visit their web sites and learn more.
I only put them in one location to make it easier for people to get the information.
Here is the dating guide for 60's and 70's Ludwig Drums.