Reused Soviet project numbers and disputed design dates

Could the conflicting Project 66 dates come from authors confusing different designations?

Reused project numbers or a revived hull design are offered as possible explanations, with Project 68 variants as an analogy; the Project 66 chronology remains disputed.

Reused project numbers are suggested as an explanation for conflicting accounts of Project 66. Alex also proposes that an earlier hull design could have returned with a different equipment fit while retaining its number. He offers Project 68 as an analogy, listing variants including 68K, 68 bis, 68 U1, and 68 U2 and dates ranging from 1939 to about 1973. These possibilities explain why a project number alone is insufficient to date a design, but the exchange does not establish which Project 66 chronology is correct.