Income Taxes - Deferred tax assets (liabilities) (Details) - USD ($)	Dec. 31, 2023	Dec. 31, 2022
Deferred Tax Assets:
Inventories	$ 254,000	$ 110,000
Accrued employees compensation and benefits costs	362,000	399,000
Postretirement obligation (accumulated other comprehensive income)	635,000	621,000
State credit carryforwards	177,000	173,000
Federal Net operating loss carryforward	1,493,000
Bad debt reserve	26,000	25,000
Warranty reserve	114,000	122,000
Research and experimental expenses	751,000	615,000
Customer accruals	344,000
Sec 163(j) disallowed interest	83,000
Other	40,000
Total deferred tax assets	4,279,000	2,065,000
Valuation allowance	(3,145,000)	(173,000)
Net deferred tax assets	1,134,000	1,892,000
Deferred tax liabilities:
Prepaid expenses	(71,000)	(70,000)
Property, plant and equipment	(853,000)	(774,000)
Other receivable - insurance proceeds	(210,000)
Total deferred tax liabilities	$ (1,134,000)	(844,000)
Net deferred tax asset		$ 1,048,000