help on ELGIN badges

[weebob]

Is the correct term button badge or bottle cap badge,I have heard both,,,or,,,,????

 

[weebob]

The ser# on this Elgin camelback is 43932,,,,no letters any where,,,where do I find elgin ser#'s or the manufacturer of this frame? present info is 1920 thru 1924 had button badges ???,,,,I found 1927-28-29 with rivet badges,,,,???? Thanks