Condensed Consolidated Income Statements - USD ($)	3 Months Ended		9 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Income Statement [Abstract]
Net revenue	$ 25,551,000	$ 27,877,000	$ 92,245,000	$ 84,204,000
Cost of goods sold	19,444,000	20,365,000	66,282,000	61,780,000
Gross profit	6,107,000	7,512,000	25,963,000	22,424,000
Operating expenses:
Product engineering and development	824,000	845,000	2,518,000	2,616,000
Selling, general and administrative	3,290,000	3,214,000	10,997,000	9,075,000
Total operating expenses	4,114,000	4,059,000	13,515,000	11,691,000
Operating income	1,993,000	3,453,000	12,448,000	10,733,000
Other income (expense), net:
Interest and dividend income, net of fees	966,000	673,000	2,485,000	1,731,000
Net realized and unrealized gains on marketable securities, net	363,000	46,000	2,087,000	2,700,000
Total other income (expense), net	1,329,000	719,000	4,572,000	4,431,000
Income before income tax expense	3,322,000	4,172,000	17,020,000	15,164,000
Income tax expense	764,000	960,000	3,914,000	3,603,000
Net income	$ 2,558,000	$ 3,212,000	$ 13,106,000	$ 11,561,000
Net income per common share - basic	$ 0.17	$ 0.22	$ 0.89	$ 0.79
Net income per common share - diluted	$ 0.17	$ 0.22	$ 0.89	$ 0.79