One-Fifth (1/5) Oz.
In the Spring of 2008, the surge in silver prices prompted the base valuation of the one-ounce silver pieces to increase to $50. This change led to additional denominations: a 2/5 ounce $20 piece, a 1/5 ounce $10 piece, and a 1/10 ounce $5 piece to accompany the $50 base one-ounce silver pieces.
The choice of increasing the one-ounce silver pieces to a $50 base in 2008 is an odd one. The silver price peaked at $20.92 on March 17th and dropped to $8.79 on October 28th, nowhere near $50. The new base could be attributed to factors other than the market price of silver at the time.
The $50 valuation may have been based on anticipated future increases in silver prices. It could also have been influenced by other market dynamics like demand for silver in industrial use or maybe it was perceived as a long-term value investment in the volatile economic environment of the 2008 financial crisis.
There may be additional variations, if you have pictures please send to brian 'at' norfed 'dot' info and I will credit you here.