China Western Wei Wu Zhu or Sui Dynasty Wu Zhu

Western Wei and Sui Dynasties have totally similar Wu Zhu coins with inner rim only next to Wu and head of Jin tilting right. Hartill codes 10.25 and 10.26. Based on Gratzer and Fishman book “One thousand years of Wu Zhu Coinage”, the only way to identify these coins are naturally find-spots and metal. Western Wei coins have a copper alloy with  a high proportion of copper and similar Sui Dynasty coins have also copper but high tin content. These coins also have some proportion of zinc and sometimes lead also. Gratzer  Fishman book does not mention how much is high content, meaning how high should be Western Wei coins' copper content and how high should be Sui Dynasty coins' tin content. I got an idea. What do you think could it be possible to measure the copper and tin content by measuring their density?

I know that the measuring is not accurate and we also have to make an assumption that those both coins have a very small proportion of zinc and or lead or at all. I made a quick test with only 5 coins (I do have some 70 of these coins). I got densities: 8578, 7415, 8764, 7578 and 8441. The higher the density is the higher should the copper content be. If these coins have only copper and tin, then you could calculate the copper contents like: 87 %, 52 %, 94 %, 57 % and 84 %. So two of these coins could have much higher copper content but is that kind of calculation and assumption reliable enough to identify two of these coins as Sui Dynasty coins with higher tin content?

Hello Olli

In the  François Thierry “les monnaies de la Chine ancienne”

attempts at analysis lead to no convincing conclusions Proportion of copper ranging from 88 to 67% for the first and from 95 to 55% for the others (differents graves dated ) the weight is not a criterion either it seems In different tombs of different age the weight ranges from 7.5g to 1.7g

Thank you Guillaume. 

So it looks like the find spot is the only strong criterion to identify these coins if copper or tin content isn't neither weight.  Does Thierry have any other way to identify these coins? 

My rough calculation gave me as low as 52 % and 57 % of copper and based on Thierry Western Wei coins should have +67 % of copper, so based on that these 2 coins could be Sui coins, or? Have you another way to identify these coins or do you just put them to either Western Wei or Sui coins?

Hello

No more information sorry

So the finding spot is the best way to know the issue cause they seems to have not really circulated really far from the place of production

Francois Thierry:

three years after their issue, these currencies do not seem to have reached the major provincial markets

Around 585 the coins all had to contain lead and tin

as pewter was cheap there were many who sought maximum profit and it became impossible to ban privately cast coins

Between 585 and 590 places that produced gossip were banned and private individuals could not obtain it

And from your question

 do you just put them to either Western Wei or Sui coins?

I sadly only have one  10.25 and one 10.26a(in poor condition)

So i did not have yet this trouble for classification 😁

Thank you very much for this additional information. Now I approximately calculate the copper content by using density measuring and also reasonance frequency which I get using my phone. Based on that calculation I put some of my coins to Sui Dynasty coins and rest (=main part) to Western Wei coins. That is the best I can do at the moment. I have already noticed that some coins are also a bit magnetic.

Previous owner has added Doo numbers to these also but I don't have that catalog. I have noticed that Doo have many numbers so there must be some minor differencies in addition to weight and diameter.