(Here's where I kinda geeked out a bit trying to date it a bit better):Based on the information on these 2 pages, and if you look at the total number of drums made between April of 1964 and April of 1965 (which was 111,076), and you divide by 12 months, that gives you an average of 9256 drums per month. If you take the serial number of this drum and subtract from the April 1964 starting point, this would be the 105,433rd drum made in that period. Taking that number and dividing by the average number of drums per month, would tell you (if the averages held) that this was probably made about 11.39 months into that cycle, giving this drum an approximate manufacture date of March 1965, maybe give or take a few weeks.
Steve,
You have made a common mistake when using the dating resources you found online. I would caution against thinking that an accurate date estimate within a few weeks is possible based upon a Ludwig serial number.
The table from which you took the April 1964 and 1965 serial numbers reports 17 specific drums that had serial numbers and date stamps (or in this case, partial date stamps). If one digs deeper, they learn that these are drums hand selected to provide some rough guidance in dating of Ludwig drums. The author explains that these are merely representative examples. When graphed, they form an almost perfectly straight line, which ignores the deviations seen in the serial number/date stamp relationship and leads many down the same path you outlined above. The author explains the limitations in an article which accompanies the tables, but many look at the tables in isolation. Many are tempted to interpolate between points in this table to develop more precise date estimates, an approach which was originally suggested by the author. While this produces a more precise estimate, increased accuracy is not achieved.
Despite the cautions I state above about the table you used, there is a fairly strong link between the dates stamped inside shells and the serial numbers on the badges of vintage Ludwig drums. There is also considerable variation in the relationship that affects any date estimate. The variation is due to a lack of strict orderly use of shells in date order and badges in numerical order. Once one understands the variations and recognises that date estimates that are both highly precise and highly accurate are not realistic, they can learn to be comfortable with date estimates with broader ranges.
Rick