Condensed Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Current Assets:
Cash and cash equivalents	$ 18,678	$ 18,331
Marketable securities	5,918	5,791
Accounts receivable, net of allowances of $191 and $189, respectively	3,913	4,122
Inventories, net	5,339	5,280
Prepaid expenses and other current assets	365	257
Total Current Assets	34,213	33,781
Property, plant and equipment:
Land	536	536
Buildings and improvements	4,822	4,810
Machinery and equipment	17,818	17,775
Gross property, plant and equipment	23,176	23,121
Less: accumulated depreciation	(20,451)	(20,336)
Net property, plant, and equipment	2,725	2,785
Right-of-use lease assets	396	422
Equity investment in unconsolidated subsidiary	5,721	3,072
Intangible assets, net	308	327
Deferred income taxes, net	3,023	3,052
Other assets	64	16
Total Assets	46,450	43,455
Current Liabilities:
Subscription agreement payable (Note C)	2,725
Accounts payable	1,517	1,265
Accrued compensation and commissions	1,491	1,324
Other accrued expenses	575	808
Total Current Liabilities	6,308	3,397
Long-term lease liabilities	272	293
Total Liabilities	6,580	3,690
Contingencies (Note N)
Stockholders’ Equity
Common stock, $0.01 par value - 10,000,000 shares authorized; 5,383,300 shares issued and 5,272,204 shares outstanding at March 31, 2021, and 5,409,550 shares issued and 5,272,204 shares outstanding at December 31, 2020	53	53
Additional paid-in capital	45,555	45,477
Accumulated deficit	(5,158)	(5,185)
Treasury stock, 81,584 shares held in treasury at cost at March 31, 2021 and December 31, 2020	(580)	(580)
Total Stockholders' Equity	39,870	39,765
Total Liabilities and Stockholders' Equity	$ 46,450	$ 43,455