I had a ponder about your discs and while I have no experience with anything Chinese – except for receiving acupuncture several times many years ago…and their food – I got curiouser and curiouser the more I looked at them.
I wasn’t really interested at all and read the topic in passing, but the imagery on the discs became a little puzzle that just needed a crack at. You did say that you thought they were currency, about 45-55mm across, and could easily be held on a thong (either about the waist, wrist or neck I would think…more likely the neck: easy to access and show someone…but then again, even easier to hang off a hat).
I’m going to offer that they are toll-discs, giving the wearer privilege of access because of the Sun-orb prolific throughout: the upright man means day/s; the on-all-fours man week; and the man reaching for the sword-on-the-branch month. (well, interchangeable of course…but the sword-on-the-branch looks more important than the others)
There are 2 kinds of upright man: facing us and facing the orb; and there are two versions of these: with mountain and without mountain. The on-all-fours man is facing the direction he is going; and the last man is facing the sword.
The obverse of 18 discs is grouped into 5 columns but there are slight differences between some in the columns, so while you may have grouped them according to their imagery of what the man is doing in his scene, the written meanings applying to those scenes are varied.
In the first column, all 4 are different. The second column are the same. The third column has 2 versions. The fourth column all 4 are different. The last column are the same.
Otherwise, considering you have shown 4 versions of the man, then this is 4 rows showing the written meanings of when these discs apply…seasons or particular months of the year or indicating particular rulers of the time or even, applying to particular access areas the wearer is free to avail themselves of.
The large discs – 20cm – are quite curious, especially the characters on the obverse side: mountain with soil beneath (top – earth); fish (left – water); gusty curl (bottom – wind); and curly fire on the right. Two kinds of scenes, though: mobile and settled.
I’m going to guess these are merchant’s/trader’s discs, used in one city by those who came to do business: the small for the trader; the large for the stall. Mobile and Settled means a merchant could move his stall according to pedestrian flow and time of day; or had to stay still.
I would guess these are the collection of one merchant or one business, left over from a certain time period when they were implemented for use for a small period of time rather than hundreds of years. I’m going to guess that maybe there aren’t that many around because for each visit, the merchant would trade the last disc and small fee for the current disc, rather than pay a larger fee for the current disc. These were then ground down to powder and either re-cast for next time or used for something else.
The discs are thick so they aren’t easily broken; and the one where the hole doesn’t go right through and has triangle forms on both sides that are separated by a thin barrier in the middle could mean that it is an unused toll-disc, unpunctured by the seller using a small tool with triangle recess to twist the centre out and make it ‘sold’. (this makes for easy accounting at the end of the day because punctured discs could not be collected back and the sellers could not defraud the city of its dues).