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Geographic Information (Detail) - Financial information about foreign and domestic operations and export sales (USD $)
 3 Months Ended 6 Months Ended
Nov. 30, 2012
Nov. 30, 2011
Nov. 30, 2012
Nov. 30, 2011
Revenues from sales to unaffiliated customers:        
Revenues from sales to unaffiliated customers $ 1,883,771 $ 1,616,606 $ 3,585,719 $ 3,024,271
United States
        
Revenues from sales to unaffiliated customers:        
Revenues from sales to unaffiliated customers 157,000 340,000 437,000 527,000
Asia
        
Revenues from sales to unaffiliated customers:        
Revenues from sales to unaffiliated customers 1,042,000 657,000 1,944,000 1,287,000
Europe
        
Revenues from sales to unaffiliated customers:        
Revenues from sales to unaffiliated customers 675,000 602,000 1,183,000 1,184,000
South America
        
Revenues from sales to unaffiliated customers:        
Revenues from sales to unaffiliated customers 2,000   2,000 1,000
Middle East
        
Revenues from sales to unaffiliated customers:        
Revenues from sales to unaffiliated customers 7,000 6,000 18,000 10,000
Other
        
Revenues from sales to unaffiliated customers:        
Revenues from sales to unaffiliated customers $ 1,000 $ 12,000 $ 2,000 $ 15,000