I've found it almost impossible to date the late (1972-75) Fullerton script Dyna's because the Dyna tags were applied in no particular order, and a lot of them were randomly put on the Dynasonic parade drums (tenor drums and bass drums!). With little dating help from the serial numbers, we can estimate the dates by some hardware features (such as the type of snare frames or the type of reso hoops on the drum).
I've recorded that Fullerton Dyna serial #30243 had a factory "Big R" snare hoop, while some Dyna's in the #40xxx range (like Chromeo's) have been spotted with rolled-over, Dayton-style snare gates. Seems to be no rhyme or reason when it comes to the serial numbers. My 6.5" Dyna #55818 naturally has the Big R style hoops as it was one of the last script Dyna's before the transition to the Big R shells. The changeover to the Big R style gates had to be around 1973-74, as the '73 catalog shows the Dayton style gates:
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I'd guesstimate that any Fullerton Dyna with Big R style gates is 1973-75, and any Fullerton with the older style gates is 1970-73. Just my :2Cents:
Mike