Balance Sheets (Current Period Unaudited) - USD ($)	Dec. 31, 2017	Mar. 31, 2017
ASSETS
Cash and cash equivalents	$ 4,728,352	$ 8,199,364
Marketable securities, short-term	18,808,203	19,591,833
Accounts receivable, net of allowance for uncollectible accounts of $15,000	2,165,866	3,436,802
Inventories	3,596,326	3,358,298
Prepaid expenses and other assets	967,958	607,283
Total current assets	30,266,705	35,193,580
Fixed assets
Machinery and equipment	9,504,983	9,007,455
Leasehold improvements	1,751,646	1,644,419
	11,256,629	10,651,874
Less accumulated depreciation and amortization	9,742,050	9,238,626
Net fixed assets	1,514,579	1,413,248
Long-term deferred tax assets	333,023	357,055
Marketable securities, long-term	56,729,730	56,810,923
Total assets	88,844,037	93,774,806
LIABILITIES AND SHAREHOLDERS’ EQUITY
Accounts payable	258,869	376,275
Accrued payroll and other	534,194	576,313
Deferred revenue		142,733
Total current liabilities	793,063	1,095,321
Shareholders’ equity
Common stock, $0.01 par value, 6,000,000 shares authorized; 4,842,010 issued and outstanding as of December 31, 2017 and 4,841,010 issued and outstanding as of March 31, 2017	48,420	48,410
Additional paid-in capital	19,599,298	19,507,348
Accumulated other comprehensive loss	(265,991)	(38,298)
Retained earnings	68,669,247	73,162,025
Total shareholders’ equity	88,050,974	92,679,485
Total liabilities and shareholders’ equity	$ 88,844,037	$ 93,774,806

Carrying value as of the balance sheet date of liabilities incurred (and for which invoices have typically been received) and payable to vendors for goods and services received that are used in an entity's business. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount due from customers or clients, within one year of the balance sheet date (or the normal operating cycle, whichever is longer), for goods or services (including trade receivables) that have been delivered or sold in the normal course of business, reduced to the estimated net realizable fair value by an allowance established by the entity of the amount it deems uncertain of collection.