Birmingham boxlocks with J. Smith, Brighton on the barrels only come in a fairly narrow range of "good, good, and better". I'd believe anything of the remuddled and scoured out sidelocks which float from owner to owner on the strength of a maker stamp and an O&L case.

Best advice: buy the gun you can afford even if it betrays your spot appraisal and hope for the best. You can't dig as deep a hole for 7C as you can for 5K.

jack