Condensed Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Current assets
Cash and cash equivalents	$ 954	$ 1,057
Investments	7,732	7,742
Trade receivables, less allowance for doubtful accounts of $11	1,075	896
Inventories	1,638	1,618
Other current assets	167	155
Income tax receivable	12	0
Total current assets	11,578	11,468
Deferred income tax asset, net	189	192
Intangible assets, net	510	565
Property and equipment, net	1,073	1,050
Total assets	13,350	13,275
Current liabilities
Current maturities of financing lease	5	5
Accounts payable	207	116
Accrued expenses	417	405
Total current liabilities	629	526
Long-term liabilities
Finance lease, net of current maturities	23	24
Total long-term liabilities	23	24
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	2,022	2,019
Retained earnings	10,304	10,335
Accumulated other comprehensive gain (unrealized gain on available-for-sale securities, net of income tax)	33	32
Total stockholders' equity	12,698	12,725
Total liabilities and stockholders' equity	$ 13,350	$ 13,275