I can confirm, they were four.
There was no other Dragon WWI Aircraft around, anyway.
The Dragon 1/48 models were pretty high quality for their time, anyway they were marred, at least when they were released for the first time, by the presence only of the photo etched struts, which were far from realistic and pretty easy to fall apart. In addition, Fokker Dr.1 wings had a forward stagger and at times also a wawy leading edge, impossible to correct.
The later re-issued models were much better, providing plastic struts and a better printing.
Some of them were reissued by revell in this century.