While educating myself this evening, I came across this clip of Simon Reinhold where he mentions the London gunmakers offering Birmingham boxlocks and mentions the J. Robertson trade name specifically.

https://youtube.com/clip/UgkxRk0y-cNuoCLfYRGovt1fOOFHohMDOIVG?si=goR3hOv31DGP4nXB

Not that confirmation from Boss & Co. wasn't enough, but it's always nice to learn more of the story behind it. Hoping to have this one in my hands by the end of the week.