Originally Posted by
WHBM
Supposition only, but I have always thought that the J61 was seen as a different aircraft to the ATP with a different type certificate
No, it was just a marketing name.
Certificating it as a new type would have been the height of folly, but the hope was presumably that the market would be fooled into believing that it was one. Needless to say, that failed, as it usually does.