The bag
I kinda suspected it wasn't the original. Looks in too good a condition to be 50's vintage, especially with the white locking collar.
As for serial numbers, a little searching on the forums here has revealled some serial numbers!
http://www.vacuumland.org/cgi-bin/TD/TD-VIEWTHREAD.cgi?3836 - post #10.
Model 119 Hoover Junior, Bronze & Dark Brown, Produced October 1950 - December 1956
Serial Numbers:
K 10,000 = October 1950
K 100,000 = january 1951
K 200,000 = June 1951
K 300,000 = November 1951
K 400,00 = May 1952
K 500,000 = December 1952
K 600,000 = July 1953
K 700,000 = December 1953
K 800,000 = May 1954
K 900,000 = December 1954
KG 100,000 = March 1955
KG 200,000 = August 1955
KG 300,000 = January 1956
KG 430,430 = July 1956 Production End
As mine is KG438852, I guess it was made in the last few months of production in '56.