My Vintage 1951 Gibson CF100

This is a vintage Gibson CF100 I was lucky enough to aquire from an older gentleman for a very cheap price...I have been told by Gibson that this is a 1951. These were made from 50-59..Can anyone shed any light on this guitar. I really would like to know how Gibson determined the year. Was it by the serial number which is clearly seen in the photo or by something else...Would love to hear from one of you Gibson collectors...