This page requires Adobe Reader. Page 2203 on the right side under Std. 16. I think it opens on 2202, but I use odd monitor settings that will change things sometimes.
https://store.bluebookinc.com/info/P.../Serialize.pdf
What the heck, I copied the info, but lost the formatting.
In 1953 Browning changed the Ser. No. alphabetic
character to differentiate between Lightweight
(Sweet 16) & Standard weight guns.
Year Std.16 Sweet 16
1953 R1-R3100 S1-S3700
1954 R3100-R20800 S3701-S24850
1955 R20801-R48750 S24851-S49350
1956 R48751-R74700 S49350-S72300
1957 R74701-R99999 S72301-S99908
1957-58 Prefix "T" for Standardweight and Prefix "A"
for Sweet 16 numbers mixed, but range from 1-
10900.
1958-1976 Ser. No. sequence changed to include
a one or two digit numeral followed by an alpha
character.