David,
Gordon's book is indeed a good resource on Leman patch boxes, and the boxes you describe are common on Lemans. Also, as Chuck says, mixed iron and brass hardware on Lemans is something that does not show up until much later. I've never seen this on a gun that predated the 1850's and it mostly shows up on the later wilted lily capbox guns of the Indian Wars era.
Also, Leman's are one of those guns that you see commonly built but poorly researched. 99% of the contemporary Lemans that are built to represent the fur trade era actually represent the Indian Wars era. Most of the pre-1840 Lemans had more in common with guns built by Dreppard or Gibbbs than with what most people see as a Leman today. After about 1840, Lemans were pretty much all Leman (re the ghost head box guns and forward). I've also never seen a lot of Fordney in Leman's guns. I've always thought he was really more influenced by George Tryon who he worked for after Fordney. The fanciest early Leman that I've seen is the one pictured in Shumway's Longrifle Articles V.1 page 162. I think the engraving style on this one is more traditional than Fordney's, but its about as close as it gets.
Sean