[Milsurplus] 618S preliminary manual publication date

[antqradio at sbcglobal.net]

Pardon the double post.
Does anyone have a copy of the preliminary instruction manual for the 618S?  The manual on the web, which is for the 618S-1/-4, has a pub date of 15 October 1957 while the preliminary manual I have for the AN/ARC-38 has a pub date of 1 June 1956.  
So if the ARC-38 is indeed a 618S with a SMO, (why else would you need a code book to set frequency?) then the 618S must be a bit older then June 1956.  Does anyone know for sure when the 618S first entered commercial service?
Any help appreciated, Jim