I have worked on the discs today, and put them into some order, hopefully with the fronts and backs of all the pieces. Obviously I would really appreciate the opinion of someone conversant with Chinese scripts. I still think they were used as currency. They show great variation in the amount of wear (which is consistent for front and back of the pieces). So here goes. There are 19 groups all told, with three types of human image (two upright one crawling)
Note the extremes of wear on these two pieces. The one on the left has never been used, hence stone used to polish out hole still in situ
Two with script, two without
Note character variation
Three with writing, two without
With C Dragon icon
Same three discs - one has turning marks, one a chip
Crawling man with Sun and C Dragon
Sun and water icons
Obverse. Again note the variation in wear
I like the fish! Note the eyes must surely have been done with a tubular metal 'bit'
The boring obverse
Two fishes being speared. Note in many of these discs there are traces of cinnabar, (mercuric sulphide) which may have been used for colouring.
Two turtles (with sun) and one pack animal
Obverse. Pack animal gets the writing
These only have script.
Obverse of same
Man, one character, and nothing on the back
You can see they vary greatly in thickness
Some odds and sods. I like the baby on the left
This is a bigger piece in ?limestone, inlaid with the same pseudoturquoise
These are greener. Top left was treated by a friend in hydrochloric acid
Three miscellaneous pieces
So there you have it. Seems entirely consistent with being the earliest ever extant currency. Please let me have your comments and observations.