Lot's of overlap on the three most common patch/cap box styles that Henry Leman used.
This early style four-piece patch box can be found on original flint and percussion rifles.
It was probably used from the late 1830s and well into the percussion period.
The 2-screw fleur-de-lis finial cap box, which is the one most identified with Leman, can be found on flintlock rifles with locks dated 1840.
It was clearly used from 1840 through the 1880s.
The use of the oval 4-screw cap box probably overlaps the 2-screw fleur-de-lis finial cap box.
Jack Brooks, who makes a bench copy of the classic Leman Indian rifle and has had many Leman rifles come through his shop for repair and restoration, has said that it almost appears that the Leman workers had buckets or bins of parts near their work bench and put on the rifle they were working on whatever they happened to grab from the bucket. In other words, he's seen rifles with a diverse mixture of parts.
Scota4570, copies of all three of these patch/cap boxes are commercially available from suppliers.
https://www.muzzleloaderbuilderssupply.com/mbs3cart/agora.cgi?cart_id=2570706.31361&next=50&product=Patchboxeshttps://www.trackofthewolf.com/Categories/PartDetail.aspx/813/1/PB-MA-10-Bhttps://www.trackofthewolf.com/Categories/PartDetail.aspx/813/2/PB-LEMAN-B