It was the final barrel-cocking recoilless Diana match rifle. Same as the mod 65 but with a squared stock. Made from 1974 until late '70s/early '80s, from 1977 simultanously with the sidelever Diana 75. The 65/66/75 used the same Giss power plant of opposing pistons, one a dummy. Value is somewhere between about £120 and £200, depending on condition, when seals were last changed, demand on the day.