Those boats are pretty rare. The Original 1965 Formula Jr. Hull mould was modified in 1969 and given a new deck (a couple of decks, actually) to make a stop-gap model for just 2 model years while a new 17 was being designed. They were available as closed deck, bow-rider, with o/b or i/o drive.
The original Jr. design was usurped by the DONZI 16 Ski Sporter in the sales arena and never really recovered. (As we know, the Donzi was wildly successful) This led to the modifications on the Jr. in order to update the look (remove the "old" looking tumblehome) and set the model apart, while appealing to other segments of the market to increase sales.