hi bigben,
with browning a-5's, Serial Numbering System changed in 1954-55. H=Standard Weight. L=Light Weight. in 1956 light wieght changed to G. the only s/n using an L was in the 55-56 years. also check for yourself at this site.
http://www.browning.com/customerservice/dategun/
detail.asp?id=13
Kim