my F5 Gibson Mandolin when was it manufactured

Hi, I would like to know if any one can tell me what year this F 5 Gibson mandolin was made in,
I was told by Gibson in Europe, that this mandolin was made some time in the 1920 or 1930 on account of the label inside that was printed,
but the serial number was stamped after. I also was told by a collector/buyer in the USA that this was a mandolin from the 1970's.
He went on to tell me that it could not be from before the 1970's , He said that if it was older then the 1970's it should have two labels on the in side.
By the way in side this mandolin there is a dry up rattlesnake tail
I would like to know what year this Gibson it was manufactured in.
Thank you