Note 1 - Summary of Significant Accounting Policies (Details Textual)	12 Months Ended
Mar. 31, 2018 USD ($)	Mar. 31, 2017 USD ($)	Mar. 31, 2016 USD ($)
Allowance for Doubtful Accounts Receivable, Current, Ending Balance	$ 35,000	$ 27,000
Inventory Valuation Reserves, Ending Balance	58,000	51,000
Other Comprehensive Income (Loss), Securities, Available-for-Sale, Unrealized Holding Gain (Loss) Arising During Period, after Tax	$ 0	$ 0	$ 54,000
Cost of Goods, Total [Member] \| Supplier Concentration Risk [Member]
Number of Suppliers	4	4
Concentration Risk, Percentage	50.00%	50.00%
Building [Member]
Property, Plant and Equipment, Useful Life	30 years
Furniture, Fixtures, Equipment and Computer Software [Member] \| Minimum [Member]
Property, Plant and Equipment, Useful Life	3 years
Furniture, Fixtures, Equipment and Computer Software [Member] \| Maximum [Member]
Property, Plant and Equipment, Useful Life	10 years

Represents the number of major suppliers of the Company.

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A valuation allowance for trade and other receivables due to an Entity within one year (or the normal operating cycle, whichever is longer) that are expected to be uncollectible.

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For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

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Amount of valuation reserve for inventory.

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Amount after tax, before reclassification adjustments, of unrealized holding gain (loss) on available-for-sale securities.

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- Definition

Useful life of long lived, physical assets used in the normal conduct of business and not intended for resale, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Examples include, but not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment.

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