question on one line address

[Hexer]

I believe that the four line address began after 1948, when did the one liners begin? In the mid 20s I am guessing. Also was it the same for all frames? Thanks in advance for the help.

 

[Hondo44]

The order for the one line "Made In U.S.A." came down in 1922 for all models.

 

[DCWilson]

And just to refine the four-line start-up date, that order came down in April 1948, with four line guns known to have shipped in May of that year. There may be some that shipped in late April, but I haven't actually seen records to prove that.