The Cogswell & Harrison pictured by Daryl has a faint "Not for Ball" stamp...and looks to have been originally proofed in London. This would make it 1887 or earlier. (This is not hard and fast... Terry Lubzinski’s side lever 12 bore Reilly has a serial number 303XX - 1889 - but with "Not for Ball.")

Parabola's camelopard is definitively 1889 per the serial number. Close but not so close that a definitive conclusion can be reached.