(A) "Prior service" means all service as a teacher before September 1, 1920, military service credit, all service prior to September 1, 1920, as an employee of any employer who comes within the public employees retirement system, the school employees retirement system, or any other state retirement system established under the laws of Ohio, and similar service in another state, credit for which was procured by a member under former section 3307.33 of the Revised Code, prior to June 25, 1945. Prior service credit shall not be granted to any member for service for which credit or benefits have been received in any other state retirement system in Ohio or for credit that was forfeited by withdrawal of contributions, unless the credit has been restored. If the teacher served as an employee in any two or all of the capacities, "prior service" means the total combined service in the capacities prior to September 1, 1920. If a teacher who has been granted prior service credit for service rendered prior to September 1, 1920, as an employee of an employer who comes within the public employees retirement system or the school employees retirement system, establishes, subsequent to September 16, 1957, and before retirement, three years of contributing service in the public employees retirement system, or one year in the school employees retirement system, the prior service credit granted shall become, at retirement, the liability of the other system if the prior service or employment was in a capacity covered by that system.