Note 3 - Segment Information - Schedule of Segment Reporting Information (Details) - USD ($) $ in Thousands		3 Months Ended																12 Months Ended
		Dec. 31, 2024		Sep. 30, 2024		Jun. 30, 2024		Mar. 31, 2024		Dec. 31, 2023		Sep. 30, 2023		Jun. 30, 2023		Mar. 31, 2023		Dec. 31, 2024	Dec. 31, 2023
Net sales		$ (653)		$ (650)		$ (531)		$ (392)		$ (446)		$ (438)		$ (403)		$ (441)		$ (2,226)	$ (1,728)
Net investment income																		(2,071)	(1,566)
Net (losses) gains		(1)	[1]	2	[1]	1	[1]	3	[1]	0	[1]	4	[1]	(43)	[1]	(345)	[1]	5	(384)
Total revenues		1,157		1,179		1,068		888		995		978		721		984		4,292	3,678
Manufacturing cost of sales		261		368		214		204		201		195		208		192		1,047	796
Engineering																		209	248
Commissions																		112	99
Sales and marketing																		185	11
Accounting																		270	339
Compensation																		1,022	591
Corporate allocations (a)	[2]																	0	0
Other segment items (b)	[3]																	748	948
Engineering, selling and administrative		651		673		617		605		465		584		645		542		2,546	2,236
Total expenses		912		1,041		831		809		666		779		853		734		3,593	3,032
Segment profit (loss)																		699	646
Income before income taxes		245		138		237		79		329		199		(132)		250		699	646
Net sales		653		650		531		392		446		438		403		441		2,226	1,728
Net investment income																		2,071	1,566
Net (losses) gains		$ 1	[1]	$ (2)	[1]	$ (1)	[1]	$ (3)	[1]	$ 0	[1]	$ (4)	[1]	$ 43	[1]	$ 345	[1]	(5)	384
Operating Segments [Member] | Electronic Instruments [Member]
Net sales																		(2,226)	(1,728)
Net investment income																		0	0
Net (losses) gains																		0	0
Total revenues																		2,226	1,728
Manufacturing cost of sales																		1,047	796
Engineering																		209	248
Commissions																		112	99
Sales and marketing																		185	11
Accounting																		0	0
Compensation																		243	224
Corporate allocations (a)	[2]																	42	35
Other segment items (b)	[3]																	145	163
Engineering, selling and administrative																		936	780
Total expenses																		1,983	1,576
Segment profit (loss)																		243	152
Net sales																		2,226	1,728
Net investment income																		0	0
Net (losses) gains																		0	0
Operating Segments [Member] | Merchant Investment [Member]
Net sales																		0	0
Net investment income																		(1,228)	(869)
Net (losses) gains																		0	0
Total revenues																		1,228	869
Manufacturing cost of sales																		0	0
Engineering																		0	0
Commissions																		0	0
Sales and marketing																		0	0
Accounting																		0	0
Compensation																		0	0
Corporate allocations (a)	[2]																	371	189
Other segment items (b)	[3]																	10	27
Engineering, selling and administrative																		381	216
Total expenses																		381	216
Segment profit (loss)																		847	653
Net sales																		0	0
Net investment income																		1,228	869
Net (losses) gains																		0	0
Segment Reporting, Reconciling Item, Corporate Nonsegment [Member]
Net sales																		0	0
Net investment income																		(843)	(697)
Net (losses) gains																		5	(384)
Total revenues																		838	1,081
Manufacturing cost of sales																		0	0
Engineering																		0	0
Commissions																		0	0
Sales and marketing																		0	0
Accounting																		270	339
Compensation																		779	367
Corporate allocations (a)	[2]																	(413)	(224)
Other segment items (b)	[3]																	593	758
Engineering, selling and administrative																		1,229	1,240
Total expenses																		1,229	1,240
Segment profit (loss)																		(391)	(159)
Income before income taxes
Net sales																		0	0
Net investment income																		843	697
Net (losses) gains																		$ (5)	$ 384

[1] During Q1 and Q2 2023, the net gains primarily relate to the sale of our investments in mutual funds managed by GAMCO Investors, Inc.

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

[3] 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.