CONDENSED CONSOLIDATED BALANCE SHEETS (Unaudited) - USD ($)	Jun. 30, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 24,099,000	$ 45,048,000
Short-term investments	6,574,000	23,766,000
Accounts receivable	22,441,000	18,886,000
Inventories	45,805,000	42,093,000
Prepaid expenses and other current assets	3,226,000	2,545,000
Total current assets	102,145,000	132,338,000
Long-term investments	56,871,000	31,772,000
Property, plant and equipment	207,814,000	200,990,000
Less accumulated depreciation and amortization	119,947,000	116,384,000
Property, plant and equipment net	87,867,000	84,606,000
Other assets and deferred charges:
Patents	1,480,000	1,539,000
Goodwill	9,730,000	9,730,000
Other	2,257,000	2,046,000
Total other assets	13,467,000	13,315,000
Total assets	260,350,000	262,031,000
Current liabilities:
Accounts payable and accrued liabilities	11,373,000	10,855,000
Accrued income and other taxes	4,070,000	419,000
Total current liabilities	15,443,000	11,274,000
Line of credit	0	0
Other non-current liabilities	11,380,000	12,887,000
Stockholders' equity:
Common stock, par value $0.10 per share; authorized 10,000 shares, issued 3,420 shares	342,000	342,000
Paid-in capital	53,020,000	52,043,000
Retained earnings	329,494,000	317,745,000
Treasury shares,1,591 at June 30, 2020 and 1,565 at December 31, 2019, at cost	(149,329,000)	(132,260,000)
Total stockholders' equity	233,527,000	237,870,000
Total liabilities and stockholders' equity	$ 260,350,000	$ 262,031,000