Serial number is C221566. The letter is part of the serial number. I don't track C prefixes too closely but yours is probably from 1951. Looks to be in nice shape. Around 1958/59 it will become a Model 10.
The closest I have to yours is s/n C155209. It shipped in 5/1950.
The closest I have to yours is s/n C155209. It shipped in 5/1950.