I think the earliest of them are probably the two or three boxes that Wallace illustrated in his Muzzle Blasts series of articles concerning RCA42. There seem to be a series of later cast, captured lid boxes which utilize an outline similar to the box lid on 42 (which of course is side opening sheet) and which possibly were developed somewhere in the Carolinas, or possibly TN? IIRC, one or two of them were archaeological remnants and there may have been one or maybe two surviving guns w/ the same box type? I think all were datable to perhaps the 1780s post-war at the earliest, or more likely 1790-1800 period or something like that. It's been a few years since I've visited this topic. Those seem to be the earliest that I recall seeing anywhere.