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Zenigata Sunae and the Kan’ei Tsūhō coins of Japan

Joel Potgieter, June 2024.

Zenigata Sunae is a very interesting site for many reasons. As far as I was able to determine, it is the largest artistic representation of a coin in the world, which is already incredible in its own right. But the stories and legends surrounding it are truly fascinating and eventually led to a unique occurrence in the world of numismatics, which is the inspiration for this article.

According to legend, this massive sand sculpture was made by the locals in a single night in 1633 to show the locals’ respect and welcome for the Lord of the Marugame Domain (which was one of the feudal domains under the Tokugawa shogunate during the Edo period). It’s a nice story, but there are a few pesky logistical issues with it, starting with - ‘How did the locals manage to craft something this big so quickly, especially in the night when they wouldn’t have been able to see much?’ Most important, however, is the fact that the coins that this structure is modelled on only entered general circulation 3 years later in 1636. Most researchers still agree that it was created during the Edo period, which lasted until 1868.

Interestingly, rumour has it that during World War 2, the Americans suspected that this sand sculpture had some sort of military importance and deployed scouts to try and find out what that was.

Image sourced from Google maps

This structure measures 122 metres by 90 metres across and has a circumference of approximately 345 metres. This sculpture was deliberately made in this oval shape so that, when viewed from the top of the nearby hill, it still looks like a round coin but with more detail visible than if it was just a perfect circle. No one is allowed to actually set foot on the site (for obvious reasons) except twice a year (or in the immediate aftermath of a typhoon) when a large group of volunteers will fix up the structure and restore it to its original shape.

Now let us take a closer look at the coins that Zenigata Sunae was modelled on. For hundreds of years, Japan had relied on imported cash coins from the Asian mainland, supplemented by (illegal) privately cast coins in Japan. But, in 1636, for the first time since a proclamation banning cash coins was issued in 987 AD (I’m not sure what happened with this proclamation, since cash coins were in circulation for hundreds of years before 1636), the government of Japan authorised a massive production of copper cash coins bearing the inscription 寛 寶 通 永 (as read from top to right on the coins), which translates as Currency [of the] Kan'ei [period]. They were inspired by the success of some coins bearing the same inscription (Kan’ei Tsūhō) which were privately issued for use in the Mito Domain of Japan in 1626 (Please see image #4 below). These earlier coins can be distinguished from the coins that were issued by the government from 1636 onwards by their font (Please see image #5). The Zenigata Sunae sand sculpture is modelled after the later coin type (1636 onwards).

Above: Image #4, 1626 to 1636 1 mon issued in the Mito Domain, obverse and reverse. Source:

Above: Image #5, the government-issued type cast from 1636 onwards, obverse and reverse. Note the differences in the bottommost character, which is the easiest way to differentiate between the two types. Source: ebay

Eighty of these copper mon coins initially equalled one monme of silver (exactly 3.75 grams). 50 silver monme equalled one gold 1 Ryō (about 17.9 grams, though they were continuously being debased in terms of their gold content). However, the value of silver continued to fall against the value of these copper coins in the years to come. At the time of issue, one of these copper coins could buy a sardine, or a mochi (see image #6) or about 200 grams of salt. For larger purchases, one would have to string together a bunch of these coins (usually a hundred per string).

Above: Image #6, a plate of mochi, a traditional Japanese kind of dumpling. Source:

Examples exist of gold and silver versions of these 1 mon coins, these were not intended for general circulation but they were probably made for special occasions and were presented to the VIPs of the day. Similar coins were minted for these reasons throughout the world even until relatively recent times. Paul Kruger is known to have presented off-metal strikes of ZAR coins to visiting diplomats and other important people. Please see images #7 and #8 below.

Above: Kan’ei Tsūhō 1 mon coin cast in gold, obverse and reverse. Source:

Above: Kan’ei Tsūhō 1 mon coin cast in silver, obverse and reverse. Source:

In 1768, new and (slightly) larger coins were issued at a value of 4 mon each, which circulated alongside the (slightly) smaller 1 mon coins. Although the coins are similar in diameter and weight, the 4 mon coins can readily be distinguished from the 1 mon coins by their reverse design. While most of the 1 mon coins have blank reverses or at most one or two characters, these 4 mon coins have a wave-like pattern (see image #7). Many different varieties of reverse inscriptions and designs exist for both denominations.

Above: Image #7, a nice example of a Kan’ei Tsūhō 4 mon coin, obverse and reverse. Source:

Recently, there has been a story circulating that someone who visited Zenigata Sunae won the lottery shortly after visiting. In a country like Japan, the general verdict was that Zenigata Sunae was the reason behind this good luck. Consequently, tourists wanted to see this site in the belief that this would also bring them good luck. Inspired by the newfound popularity of the sand coin, in 2010 the city of Kan-onji decided to allow the Kan’ei Tsūhō coins to once again be made legal tender at the updated value of 30 yen apiece (about R3.44 at the time of writing). I’m not sure if only the 1 mon coins are legal tender or if the 4 mon coins are legal tender as well. It's possible that (because they are so similar in size) they are both spendable at 30 yen each in the city of Kan-onji

So that is how a giant artwork made of sand modelled on a coin with a very interesting history created a unique occurrence in the world of numismatics: a type or series of coins that were minted hundreds of years ago and was, in due time, discontinued and replaced, was recently officially returned to general circulation at a different value to what they were initially worth. These were the same coins that were cast so many years ago, not restrikes or replicas. Where else in the world today can you legally spend an almost 400-year-old coin at any shop within a given city?

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