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Note 8 - Shareholders' Equity (Tables) | 9 Months Ended
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Sep. 30, 2017
Notes Tables |
Schedule of Potential Per Share Dividend Amounts Quarterly Price Levels [Table Text Block] |
Quarterly average realized silver price per ounce |  |  | Quarterly dividend per share |  |  | Annualized dividend per share |
$ | 30 |  |  | $ | 0.01 |  |  | $ | 0.04 |
$ | 35 |  |  | $ | 0.02 |  |  | $ | 0.08 |
$ | 40 |  |  | $ | 0.03 |  |  | $ | 0.12 |
$ | 45 |  |  | $ | 0.04 |  |  | $ | 0.16 |
$ | 50 |  |  | $ | 0.05 |  |  | $ | 0.20 |

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- References No definition available. + Details
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