Underwonder asked:
"Picture 13 with brass circles in leather? Any ideas about what they are from?"
They are copper rivets, made to hold two thick pieces of leather together (like the bread in a sandwich). Corrosion of the copper in the ground produces Copper Oxide, which is toxic enough to kill the bacteria/mold and anything else that tries to eat the leather. That is why copper/brass rivets are often dug with some of the original leather surrounding them. The same thing happens occasionally with buttons, and buckles/boxplates, except with the latter the bacteria-killing chemical is Lead Oxide.
You asked what they are from. Answer: Lots of leather objects (particularly horsegear), harnesses, saddlebags, luggage, as well as military cartridge-boxes, etc. No way to tell with those rivets... unless you dig a clue like a cartridge-box finial right among them.