Quote:

The Loree serial numbers began in the late 19th century with single letter
followed by numbers: A1 - Z99 (1910). Then, from 1910 to 1930, loree serail
numbers all began with double letters, so: AA1- AA99, then BB1 to BB99, on
until ZZ in 1930. Beginning in 1930, the serial numbers changed to two
consecutive letters at the beginning: AA1-A99, then AB1-AB99, AC1 to AC99
until present day.
So, in the modern instruments there will be a duplication of serial numbers.
"GG" was circa 1925, and the modern GG series was from the mid-1980s. This
can be confusing, though the keywork patterns will always be different old
from the new. Check the shape of the F key for instance on the GG English
horn. It is narrower than the modern F key.