So while I am finishing up my Covid lock-down (thankfully COVID wasn't too bad for me.)   I though I would publish at-least one more historical paper on confusing things to hopefully make them less confusing. The Previous Article:     Today's subject is the J-2 Engine. Like most of you I know of many J-2 variants,   and confusingly many of them have the same name.   Or multiple engines have the same name with a different suffex. But we should start at the start.  
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