"Battleship" Potempkin was a large man in Chicago, Illinois in 1927 who was hired by the gangster Arnie "Eggs" Benedict as a muscle man. Along with "Mugsy" Tannen, they kept the brewmaster "Bathtub Jim" McFly from leaving the organization.
Marty staged a fake police raid using sound effects with a key ring from 1991. This allowed Doc to get the distilled juniper berries he needed to cure the eye infection from which his dog Einstein suffered. It also allowed Marty to free his relative Jim McFly from being employed by gangsters.
"Mugsy Tannen" had looked into "Zipper" McFly and discovered that no one on the east coast had ever heard of him. After the success of Marty's fake police raid, Benedict believed that the information was faulty, and told Potempkin to take care of Tannen.