N.H. Rev. Stat. Ann. § 261:91-a

The director is authorized to adopt rules pursuant to RSA 541-A for the design, sale, and distribution by towns and cities celebrating the centennial, bicentennial, tricentennial, sesquicentennial, or sestercentennial of the founding of the town or city or similar special occasion in the history of the town or city, and the display of said plates in place of the front license plate on vehicles for a period not to exceed one year, during which the celebration is taking place.