Author Topic: Lead unofficial cash of Canh Hung, Vietnam  (Read 245 times)

0 Members and 1 Guest are viewing this topic.

Offline bgriff99

  • Meritorious Member
  • ****
  • Posts: 581
Lead unofficial cash of Canh Hung, Vietnam
« on: January 25, 2018, 12:43:37 AM »
The Canh Hung reign was from 1740-86.    This is probably an unofficial issue from the late 1700's, during the Tayson Rebellion.

Offline THCoins

  • Moderator
  • Honorary Member
  • *****
  • Posts: 4 866
Re: Lead unofficial cash of Canh Hung, Vietnam
« Reply #1 on: January 25, 2018, 06:20:27 PM »
The small hole is a casting defect ?
Interesting patina for a lead coin. Looks a lot different from the surfaces i know from lead Indian coinage. Probably a consequence of both different alloys and different environmental influences i'd think.

Offline bgriff99

  • Meritorious Member
  • ****
  • Posts: 581
Re: Lead unofficial cash of Canh Hung, Vietnam
« Reply #2 on: January 26, 2018, 10:24:41 AM »
The hole is from a casting flaw, but may also have been a broken-loose bit from separating coins stuck together.    The surface has some copper mineralization, transferred from adjacent coins.    The yellowish material may also be from another coin, perhaps of zinc.     When coins of different metals like lead, copper and zinc get mixed and buried in a warm wet environment, to say nothing of saltwater, whole coins can be dissolved and re-deposited.    The blue-black surface is lead sub-oxide, or a sulfide.    Other coins in contact with it preferentially went to oxides and carbonates.

This piece is not bend-able, so has some tin or other metal.    The color looks like that of zinc and lead mixes.   It even has a slight ring.   But I cut into the edge to check metal.   It's mainly lead.    About Indian coins of lead, I see them sometimes with red mineral color, which is never seen on east Asian ones.   

Offline THCoins

  • Moderator
  • Honorary Member
  • *****
  • Posts: 4 866
Re: Lead unofficial cash of Canh Hung, Vietnam
« Reply #3 on: January 26, 2018, 01:21:18 PM »
Quote
About Indian coins of lead, I see them sometimes with red mineral color

Yes, that's my experience also, while green/blue is very uncommon for Indian lead specimen.