Engraving
These designs varied. Some manufacturers, like Conn, had their own custom engraving department and for a price would do extra work. Often, the designs were standardized (such as the Conn "Lady") and represented some kind of logo for the company. For the most part, by the 1960's or so, the elaborate engraving was a thing of the past, though one can still see some pretty elaborate stuff on some high end makes of smaller instruments such as the Shires trombones or custom trumpets.
For a while, Besson/Boosey & Hawkes used a stamped logo (the Round Stamp of the mid-70's to mid-80's) instead of an engravied logo. These days, the engraving on bells is mostly done using laser etching. Much cleaner and more uniform, but generally a much smaller engraving.
Doug
Adams E3 0.60 Sterling bell - Prototype top sprung valves
Concord Band
Winchendon Winds
Townsend Military Band