This is the first number 72 from about 1958 or 1959. Not many were made, they are rather difficult to find. It contains 72 crayons but only 64 colors, that is all Crayola made at the time. Addition black, blue and red crayons were added to make 72.
This is the second version of the number 72, it was sold from 1960 to 1962. This is the first set with the booklet copyrighted 1958.
This is the third box, similar to the second with a bigger window. It was sold from 1963 to 1966.
This is the fourth box in the series. Gone is the window, it also reflects the updated packaging used by Crayola at the time. Still only 64 colors, it was sold from 1967 to 1972.
The fifth box in the series finally went to 72 different colors with the addition of the 8 new fluorescent color introduced by Crayola in 1972. One can also tell if the set is an early or late version of this series. The fluorescent crayons in the early version had black wrappers, in the later versions the fluorescent crayons had colored wrappers. This was also the last number 72 to included the coloring booklet. This set was sold through 1976.
Crayola made some changes for the number 72 set in 1974. Instead of the paper slots to hold the crayons, this set came with three boxes of 24 crayons and 4 plastic stands for the crayons. A new 16 page project booklet replaced the previous booklet. This sixth version of the number 72 was sold from 1974 to 1978. Sales of this set overlapped the previous set.
This is seventh and final version of the number 72 set. It's basically the same as the previous set, just a new box design. This set was sold from 1979 to 1984 when Crayola upped the number of crayons to it's largest set to 96. 72 crayon sets after this set came in a plastic crayon holder and were no longer referred as the number 72 set.
I current own 5 of the 72 sets, I don't have the first or last set. 3 of them are unopened too. I would like to thank Ed Welter for much of the information used in this post. Visit his site here.