Condensed Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Current assets
Cash and cash equivalents	$ 4,620	$ 1,090
Investments	5,041	8,041
Trade receivables, less allowance for doubtful accounts of $11	1,325	957
Inventories	1,477	1,572
Other current assets	207	170
Income tax receivable	0	26
Total current assets	12,670	11,856
Deferred income tax asset, net	270	246
Intangible assets, net	50	228
Property and equipment, net	919	989
Total assets	13,909	13,319
Current liabilities
Current maturities of financing lease	6	6
Accounts payable	175	197
Accrued expenses	629	330
Accrued income tax	85	0
Total current liabilities	895	533
Long-term liabilities
Financing lease, net of current maturities	8	12
Total long-term liabilities	8	12
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	2,040	2,036
Retained earnings	10,627	10,398
Accumulated other comprehensive gain (unrealized gain on available-for-sale securities, net of income tax)	0	1
Total stockholders' equity	13,006	12,774
Total liabilities and stockholders' equity	$ 13,909	$ 13,319