Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Current assets
Cash and cash equivalents	$ 1,090	$ 8,785
Treasury bills	7,999	0
Equity securities	42	45
Trade receivables, less allowance for doubtful accounts of $11	957	1,036
Inventories	1,572	1,695
Other current assets	170	159
Income tax receivable	26	0
Total current assets	11,856	11,720
Deferred income tax asset	246	203
Intangible assets, net	228	489
Property and equipment, net	989	1,063
Total assets	13,319	13,475
Current liabilities
Current maturity of financing lease	6	5
Accounts payable	197	129
Accrued expenses	330	431
Total current liabilities	533	565
Long-term liabilities
Financing lease, net of current maturities	12	19
Total long-term liabilities	12	19
Commitments and contingencies
Stockholders' equity
Common stock par value $0.10 per share; authorized 10,000,000 shares; 3,395,521 shares issued and outstanding	339	339
Additional paid-in capital	2,036	2,030
Retained earnings	10,398	10,522
Accumulated other comprehensive gain (unrealized gain on available-for-sale securities, net of income tax)	1	0
Total stockholders' equity	12,774	12,891
Total liabilities and stockholders' equity	$ 13,319	$ 13,475