Note 3 - Segment Information - Schedule of Segment Reporting Information (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Net sales		$ 661	$ 650	$ 1,650	$ 1,573
Net investment income		442	531	1,287	1,568
Net gains (losses)		5	(2)	13	(6)
Total revenues		1,108	1,179	2,950	3,135
Manufacturing cost of sales		312	368	760	786
Engineering		74	54	188	141
Commissions		12	20	52	75
Sales and marketing		47	52	139	132
Accounting		49	39	174	227
Compensation		132	378	589	774
Corporation allocations (a)	[1]	0	0	0	0
Other segment items (b)	[2]	362	130	918	546
Engineering, selling and administrative		676	673	2,060	1,895
Total expenses		988	1,041	2,820	2,681
Segment profit (loss)		120	138	130	454
Income from operations before income taxes		120	138	130	454
Segment Reporting, Reconciling Item, Corporate Nonsegment [Member]
Net sales		0	0	0	0
Net investment income		168	213	504	646
Net gains (losses)		5	(2)	13	(6)
Total revenues		173	211	517	640
Manufacturing cost of sales		0	0	0	0
Engineering		0	0	0	0
Commissions		0	0	0	0
Sales and marketing		0	0	0	0
Accounting		49	39	174	227
Compensation		74	309	423	585
Corporation allocations (a)	[1]	(158)	(88)	(366)	(233)
Other segment items (b)	[2]	321	85	777	432
Engineering, selling and administrative		286	345	1,008	1,011
Total expenses		286	345	1,008	1,011
Segment profit (loss)		(113)	(134)	(491)	(371)
Electronic Instruments [Member] | Operating Segments [Member]
Net sales		661	650	1,650	1,573
Net investment income		0	0	0	0
Net gains (losses)		0	0	0	0
Total revenues		661	650	1,650	1,573
Manufacturing cost of sales		312	368	760	786
Engineering		74	54	188	141
Commissions		12	20	52	75
Sales and marketing		47	52	139	132
Accounting		0	0	0	0
Compensation		58	69	166	189
Corporation allocations (a)	[1]	13	10	35	29
Other segment items (b)	[2]	41	33	119	101
Engineering, selling and administrative		245	238	699	667
Total expenses		557	606	1,459	1,453
Segment profit (loss)		104	44	191	120
Merchant Investment [Member] | Operating Segments [Member]
Net sales		0	0	0	0
Net investment income		274	318	783	922
Net gains (losses)		0	0	0	0
Total revenues		274	318	783	922
Manufacturing cost of sales		0	0	0	0
Engineering		0	0	0	0
Commissions		0	0	0	0
Sales and marketing		0	0	0	0
Accounting		0	0	0	0
Compensation		0	0	0	0
Corporation allocations (a)	[1]	145	78	331	204
Other segment items (b)	[2]	0	12	22	13
Engineering, selling and administrative		145	90	353	217
Total expenses		145	90	353	217
Segment profit (loss)		$ 129	$ 228	$ 430	$ 705

[1] The Electronic Instruments and Merchant Investment segments are allocated overhead expenses from the Corporate segment based on each segment's asset as a percentage of Total assets.

[2] Other segment items for each reportable segment includes the following: Electronic Instruments - rent, amortization, professional service fees, and certain other overhead expenses. Merchant Investment - legal expense and certain other overhead expenses. Corporate - legal expense, insurance expense, filing fees, fees paid to MtronPTI under Amended and Restated Transitional Administrative and Management Services agreement, and certain other overhead expenses.