How the characteristic little lumps were produced, is unknown. One theory has it that it was done by scattering ants on the hot metal and that the formic acid caused the typical raised bumps.
However, the warts are much too regularly to have been produced in that way. In 1707, Lan Chang divided into the two kingdoms of Luang Prabang and Vientiane.
Both adopted the lat currency and continued to issue such ingots until the end of the 19th century. I never clean a coin! Maybe someone will know the mint mark. The item "Tiger-Tongue Money from Laos, Kingdom of Luang Prabang, Lat Money" is in sale since Sunday, March 6, 2016. This item is in the category "Coins & Paper Money\Coins\ World\Asia\Other Asian Coins".The seller is "donandmaureen" and is located in Babylon, New York. This item can be shipped to United States, Canada, United Kingdom, Denmark, Romania, Slovakia, Bulgaria, Czech republic, Finland, Hungary, Latvia, Lithuania, Malta, Estonia, Australia, Greece, Portugal, Cyprus, Slovenia, Japan, Sweden, Indonesia, Belgium, France, Hong Kong, Ireland, Netherlands, Poland, Spain, Italy, Germany, Austria, Singapore, Norway, Saudi arabia, United arab emirates, Bahrain, Croatia, Malaysia, Chile, Colombia, Bahamas, Viet nam, Thailand, Switzerland, Ukraine, Qatar, Kuwait, Brazil, Uruguay, China, South Korea, Taiwan, South africa, Israel, Mexico, New Zealand, Philippines, Bangladesh, Brunei darussalam, Ecuador, Egypt, Jordan, Sri lanka, Luxembourg, Monaco, Macao, Maldives, Nicaragua, Oman, Peru, Pakistan, Paraguay.