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Note 4 - Inventories (Tables)
12 Months Ended
Dec. 31, 2018
Notes Tables  
Schedule of Inventory, Current [Table Text Block]
   
December 31,
 
   
2018
   
2017
 
                 
Raw materials
  $
4,732,000
    $
4,567,000
 
Work in process
   
825,000
     
1,058,000
 
Finished goods
   
4,321,000
     
4,624,000
 
    $
9,878,000
    $
10,249,000