Original plate from Criterion made of cast aluminum. In checking Sky and Telescope sources it appears that the Dynascope 12 was available from the 1950's until 1963. In January 1963 The Dynascope was listed available in "Your choice of 6, 8, 10, 12 and 16 inch models within the magazine." The Feb & March 1963 issues featured advertising of the 6 inch RV-6 Dynascope inside the back cover. However both of the same additions; Feb & , March 1963 shows that a 12.5 inch mirror from Criterion at F-7 is available for $ 299 under more Criterion advertising within those same issues. The April 1963 edition again featured the Dynascope in 6, 8, 10 12, and 16 inch models. New to the May 1963 Sky & telescope are Custom Dynascopes in your choice of 6, 8,10, 12.5 or 16 inch models. Therefore - perhaps it maybe assumed this was about the time of the change over to the 12.5 inch Dynascope. Incidently the new 12.5 inch Deluxe Dynascope was priced $ 1265.00 from the factory at 331 Church St, Hartford, Conn. per said advertisement.