# Hoei Koban: New Findings on Gold Content Variation
The Hoei koban is a gold coin minted in Hoei 7 (1710), with gold fineness traditionally reported at approximately 83.7%. However, recent non-destructive testing using the latest portable X-ray fluorescence (XRF) analysis equipment has revealed that individual specimens exhibit considerable variation in fineness.
The investigation was conducted in cooperation with domestic university research laboratories and coin dealers, examining a total of 15 Hoei koban specimens. Analysis results showed that gold content ranged from 80.2% to 85.1%, with an average value of 83.2%. While the conventional literature value of 83.7% is essentially valid, the individual variation proved to be significantly larger than anticipated.
The research team attributes this variation to the limitations of alloy preparation techniques at the Edo-period gold mint (Kinza). During the Edo period, the Kinza combined gold and silver by hand, making it technically difficult to produce completely uniform alloys. Particularly in early production batches, fineness may have been unstable due to trial-and-error processes.
The Hoei koban was issued to raise funds for reconstruction following the Hoei earthquake and Mount Fuji eruption of Hoei 4 (1707). The issuance period was brief, lasting approximately three years, with total mintage limited to approximately 1.02 million ryo. The exact number of surviving specimens remains unclear, though it is estimated at several hundred pieces.
Regarding implications for authentication, the analysis results demonstrate that individual fineness variations should not serve as determining factors in authentication judgments. In other words, slightly lower fineness alone cannot immediately be taken as evidence of counterfeiting, and comprehensive examination is necessary.
As Ichitendo, we evaluate this research as providing important reference data for Hoei koban authentication. By utilizing both scientific analysis and traditional connoisseurship, more precise authentication becomes possible. Given the Hoei koban's rarity, historical significance, and investment value, appropriate evaluation based on reliable data will contribute to healthy market development.
Source: https://www.ginzacoins.co.jp/