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Note C - Shareholders' Equity (Details Textual) - USD ($) |  | 6 Months Ended | 12 Months Ended |
--- | --- | --- | --- | ---
Apr. 25, 2017 | Jun. 30, 2019 | Dec. 31, 2018 | Jun. 30, 2018 | Dec. 31, 2017 | Sep. 30, 2019 | Sep. 30, 2018 | Sep. 30, 2017 | Nov. 13, 2014
Stock Repurchase Program, Remaining Authorized Repurchase Amount |  |  |  |  |  | $ 5,409,326 |  |  | $ 8,000,000
Stock Repurchase Program, Increase in Authorized Amount | $ 4,000,000 |  |  |  |  |  |  |  |
Stock Repurchase Program, Authorized Amount | $ 12,000,000 |  |  |  |  |  |  |  |
Common Stock, Shares Authorized |  |  |  |  |  | 50,000,000 | 50,000,000 |  |
Common Stock, Par or Stated Value Per Share |  |  |  |  |  | $ 0.01 | $ 0.01 |  |
Preferred Stock, Shares Authorized |  |  |  |  |  | 500,000 | 500,000 |  |
Preferred Stock, Shares Issued, Total |  |  |  |  |  | 0 | 0 |  |
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant |  |  |  |  |  | 851,134 |  |  |
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount, Total |  |  |  |  |  | $ 2,371,309 |  |  |
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition |  |  |  |  |  | 4 years 328 days |  |  |
Share-based Payment Arrangement, Expense |  |  |  |  |  | $ 1,729,025 | $ 2,003,207 | $ 2,319,975 |
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross |  |  |  |  |  | 172,000 | 108,000 | 0 |
Share-based Compensation Arrangement by Share-based Payment Award, Expiration Period |  |  |  |  |  | 4 years |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period |  |  |  |  |  | 3 years | 3 years |  |
Share-based Compensation Arrangements by Share-based Payment Award, Options, Grants in Period, Weighted Average Exercise Price |  |  |  |  |  | $ 12.17 | $ 13.37 |  |
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Remaining Contractual Term |  |  |  |  |  |  | 4 years 255 days |  |
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Remaining Contractual Term |  |  |  |  |  | 2 years 146 days | 1 year 324 days |  |
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Exercisable, Number |  |  |  |  |  | 36,000 | 0 |  |
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period |  |  |  |  |  | 7,750 | 8,450 |  |
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period, Intrinsic Value |  |  |  |  |  | $ 81,728 | $ 75,767 |  |
Stock Repurchased During Period, Shares |  |  |  |  |  | 40,933 | 41,989 |  |
Treasury Stock Acquired, Average Cost Per Share |  |  |  |  |  | $ 13.51 | $ 11.66 |  |
Payment, Tax Withholding, Share-based Payment Arrangement |  |  |  |  |  | $ 553,165 | $ 489,428 | $ 952,832 |
Employee Stock Purchase Plan [Member] |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant |  | 49,846 |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Market Price Percentage, Offering Date |  |  |  |  |  | 85.00% |  |  |
Stock Issued During Period, Shares, Employee Stock Purchase Plans |  | 19,923 | 17,312 | 15,932 | 14,242 |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Purchase Price |  | $ 8.43 | $ 8.43 | $ 9.39 | $ 10.41 |  |  |  |
Payment, Tax Withholding, Share-based Payment Arrangement |  |  |  |  |  | $ 80,708 |  |  |
Director [Member] |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Remaining Contractual Term |  |  |  |  |  | 6 years |  |  |
Share-based Payment Arrangement, Option [Member] | Director [Member] |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period |  |  |  |  |  | 1 year |  |  |
Share-based Payment Arrangement, Option [Member] | Minimum [Member] |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period |  |  |  |  |  | 3 years |  |  |
Share-based Payment Arrangement, Option [Member] | Maximum [Member] |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period |  |  |  |  |  | 5 years |  |  |
Cashless Method Stock Option Exercised [Member] |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period |  |  |  |  |  | 6,750 | 2,250 |  |
Restricted Stock [Member] | Minimum [Member] | Employees [Member] | Stock Compensation Plan 2007 [Member] |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period |  |  |  |  |  | 1 year |  |  |
Restricted Stock [Member] | Maximum [Member] | Employees [Member] | Stock Compensation Plan 2007 [Member] |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period |  |  |  |  |  | 10 years |  |  |
Selling, General and Administrative Expenses [Member] |  |  |  |  |  |  |  |  |
Share-based Payment Arrangement, Expense |  |  |  |  |  | $ 1,638,829 | $ 1,835,086 | 2,103,621 |
Cost of Sales [Member] |  |  |  |  |  |  |  |  |
Share-based Payment Arrangement, Expense |  |  |  |  |  | $ 90,196 | $ 168,121 | $ 216,354 |
Undesignated Shares [Member] |  |  |  |  |  |  |  |  |
Preferred Stock, Shares Authorized |  |  |  |  |  | 5,000,000 |  |  |
Series B Preferred Stock [Member] |  |  |  |  |  |  |  |  |
Preferred Stock, Shares Authorized |  |  |  |  |  | 500,000 |  |  |
Preferred Stock, Shares Issued, Total |  |  |  |  |  | 0 |  |  |

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