Statements of Cash Flows (Unaudited) - USD ($)	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Cash flows from operating activities:
Net income	$ 3,371,375	$ 3,769,048
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	129,625	143,896
Net (gain) loss on marketable securities	(369,542)	54,261
Loss from trade-in of equipment		12,837
Deferred income taxes	(18,847)	(11,825)
Increase (decrease) in operating assets:
Accounts receivable	53,659	217,242
Inventories	208,159	(125,195)
Prepaid expenses and other current assets	(11,204)	16,248
Prepaid income taxes	102,376	(5,427)
Other assets		15,000
Increase (decrease) in operating liabilities:
Accounts payable	121,048	(231,311)
Accrued expenses	40,364	109,544
Income taxes payable	0	(55,848)
Net cash provided by operating activities	3,627,013	3,908,470
Cash flows from investing activities:
Acquisition of property, plant and equipment	(104,662)	(66,500)
Proceeds from sale of marketable securities	11,359,973	4,947,370
Purchases of marketable securities	(11,112,930)	(6,497,347)
Net cash provided by (used in) investing activities	142,381	(1,616,477)
Cash flows from financing activities:
Dividends paid	(2,524,946)	(2,291,294)
Net cash used in financing activities	(2,524,946)	(2,291,294)
Net increase in cash and cash equivalents	1,244,448	699
Cash and cash equivalents at beginning of period	550,135	724,721
Cash and cash equivalents at end of period	1,794,583	725,420
Non-cash investing activities:
Cost of equipment traded in (net)		39,837
Supplemental disclosure of cash flow information:
Taxes paid	800,000	1,075,000
Supplemental disclosure of non-cash dividends payable	$ 1,930	$ 5,866