Condensed Consolidated Statements of Income - USD ($)	3 Months Ended		9 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Income Statement [Abstract]
Net revenue	$ 24,919,000	$ 22,940,000	$ 65,235,000	$ 66,963,000
Cost of goods sold	19,314,000	17,555,000	50,504,000	49,920,000
Gross profit	5,605,000	5,385,000	14,731,000	17,043,000
Operating expenses:
Product engineering and development	1,176,000	849,000	3,089,000	2,304,000
Selling, general and administrative	3,202,000	2,522,000	10,235,000	7,465,000
Total operating expenses	4,378,000	3,371,000	13,324,000	9,769,000
Operating income	1,227,000	2,014,000	1,407,000	7,274,000
Other income (expense), net:
Interest and dividend income, net of fees	306,000	512,000	1,437,000	1,907,000
Net realized and unrealized gains (losses) on marketable securities	1,386,000	2,888,000	4,873,000	(1,465,000)
Other	0	(10,000)		(20,000)
Other income (expense),net	1,692,000	3,390,000	6,310,000	422,000
Income before income tax expense	2,919,000	5,404,000	7,717,000	7,696,000
Income tax expense	584,000	1,082,000	1,543,000	1,540,000
Net income	$ 2,335,000	$ 4,322,000	$ 6,174,000	$ 6,156,000
Basic Income per Common Share:
Net income per share	$ 0.16	$ 0.30	$ 0.42	$ 0.42
Diluted Income per Common Share:
Net income per share	$ 0.16	$ 0.29	$ 0.42	$ 0.42