Vintage RCA Victor Model C-503 Radio Clock Instructions. This manual is a rare find for collectors of vintage audio and video equipment. It provides detailed instructions on how to use the RCA Victor Model C-503 radio clock, which was manufactured in Canada. The clock is a unique piece of consumer electronics that is sure to impress any vintage enthusiast. The manual covers all aspects of the clock's features and functions, making it an essential accessory for anyone looking to get the most out of their RCA Victor Model C-503 radio clock.