You are probably talking about a bung-sided keg. Prior to the SANKE coupler, Golden Gate and later Hoff-Stevens kegs had a hole in the side which was used for filling/cleaning and sometimes dry hopping in the keg. A wooden bung is hammered into the hole in the keg side... dry hops are sometimes bagged and tacked to the bung before it goes in the keg. Many Hoff-Stevens kegs have had the original fitting removed and a SANKE type put in it's place. SABCO used to do A LOT of those conversions.
Can you post a pic of the keg side and the top?
