Use the code wheel to spell out the event.
Example
Date: March 1965
Rule: Multiply by 2
Event: 24-10-15-21-8-27-15-16-10
Solution: Look on Code Wheel
48-20-30-42-16-54-30-32-20
S T A M P * A C T
1. December 1773 Rule: Divide by 2
Event: 4 - 88 - 96 - 40 - 30 - 86 - 58 - 98 - 10 - 60 - 116 - 32 - 2 - 36 - 40 - 50
2. June 1775 Rule: Subtract 8
Event: 39 - 58 - 22 - 48 - 42 - 26 - 66 - 45 - 17 - 20 - 49
3. July 1776 Rule: Multiply By 2
Event: 2 - 17 - 16 - 6 - 15 - 9 - 15 - 10 - 19 - 22 - 7 - 29 - 22 - 3 - 29 - 19 - 7 - 2 - 17 - 18 - 17 - 7 - 2 - 17 - 7 - 16 - 17
4. July 1789 Rule: Multiply By 2, Subtract 1
Event: 22 - 8 - 24 - 25 - 19 - 12 - 3 - 10 - 25 - 15 - 8 - 24 - 17 - 5 - 22 - 1 - 22 - 2 - 3
5. April 1775 Rule: Multiply By 2, Add 3
Event: 10 - 28 - 8 - 17 - 3 - 20 - 2 - 23 - 6 - 20 - 13 - 13 - 3 - 20 - 20 - 28 - 9 - 2 - 9 - 22 - 28 - 23 - 1 - 15