A state audit released Tuesday showed that at least 125 firearms are missing from the J.M. Davis Arms & Historical Museum.
The report also found, among other things, that the museum's director didn't follow policy for receiving donated guns and that a current inventory wasn't kept.
Rogers County District Attorney Gene Haynes, who requested the audit, said further investigation is needed to determine how the guns disappeared.
"I kind of doubt that the general public could go in and shoplift a gun," Haynes said. "I think it's more likely going to be people who had authorized access to them."
The disappearances may have started as early as 1969, Haynes said. Some guns in the collection, which isn't insured, are valued at up to $50,000, Haynes said.
The official tally of missing guns was far fewer than the thousands officials initially feared. The collection should have 13,454 firearms.
The collection contains such rare items as a 500-year-old Chinese hand-cannon and the world's smallest automatic pistol, the Kolibri. Haynes said those pieces are not missing.
The collection was acquired by Claremore hotel owner John Monroe Davis, who transferred ownership to a trust called the J.M. Davis Foundation in 1965. The foundation entered into a $1 long-term lease with the state that requires the state to house, preserve and display the collection with no admission charge.
In a statement released Tuesday, J.M. Davis Memorial Commission Chairman William Higgins said museum officials are implementing the audit's recommendations, including regular inventories and an upgrade of policies to ensure donations are properly recorded and deposited.
Claremore Police Chief Mickey Perry said his department and the district attorney's office will continue to investigate whether the guns were stolen internally or externally.
"It's going to be difficult, if not impossible to trace some of these," Perry said.