This probably dates the introduction of at least the Lyman Ivory Front and Rear Sights to 1895, which is the date of the Hibbard, Spencer, Bartlett & Co. catalog listing
August 3, 1895 Sporting Life
https://digital.la84.org/digital/collection/p17103coll17/id/48503/rec/1

[Linked Image from photos.smugmug.com]

I haven't found an advertisement or catalog listing for another maker of ivory front and rear sights until Marble's c. 1930

[Linked Image from photos.smugmug.com]

I have a collection of advice for Live Bird and Inanimate Target shooters here, from 1893 to 1925
Several observe the importance of practice mounting and being sure to look straight down the rib, but no one mentions use of a center bead
https://docs.google.com/document/d/17__6nT2u4mP22we08yCBThQ_a-VtmOueW5CisK3c2To/edit

I suspect it became more popular with the transition from the Live Bird "ready" position to Inanimate Target pre-mounted position.

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