The Shelby cycle history page
does refer to Shelby making bicycles for the Chicago Cycle Supply Co.
Shelby Steel Tube Co. 1891 Lozier-Yost Seamless Tube Works, then The Shelby Steel Tube Co. formed Lozier and Yost and bring technology back from England Jonas Feighner and Capt. D.L. Cockley raised $37,500 from Shelbians toward the venture. Among original board members are J.A. Seltzer, Shelby...
shelbycyclehistory.org
It also shows various fits and starts of the company, and even a Mead (see sprocket) connection.
Maybe the “A” serial numbers might start in 1923?
Shelby Kicks Off America 250 Celebration with New Exhibit: Ohio Firsts – Shelby Steel Tube Company The City of Shelby is proud to launch its America 250 celebration with a brand-new exhibit, Ohio Firsts: Shelby Steel Tube Company, opening November 1 in the Shelby Justice Center. Created by the...
shelbycyclehistory.org
Or was it like 1925-A, and skipping some letters such as “L” and maybe “I”?