How many battalions were at Parris Island

I am a Viet Nam era Marine 1963 to 1969. I was talking to a son of a Marine that was in the Corps before me. He then pulled out a graduation book to show me his fathers pictures. First thing I noticed was in the front of the book there was no picture of the present Commandant or anything referencing any dates at all. What it did say was that there were 5 battalions at Parris Island. I knew of 3 battalions were for the men and the 4th is for women, but I hadn't heard of 5 battalions. Does anybody know what the fifth battalion was designated to, and any idea what time period this all took place. All I could surmise was that the amount of troops that were going through at the time must have demanded another battalion. Thanks. Botch (Sgt of Marines)