Property, Plant and Equipment - Summary of property, plant and equipment (Details) - USD ($)	Mar. 31, 2024	Dec. 31, 2023
Property, Plant and Equipment
Property, plant and equipment, Gross	$ 24,208,000	$ 24,056,000
Less accumulated depreciation and amortization	(17,349,000)	(17,078,000)
Property, plant and equipment, net	6,859,000	6,978,000
Buildings and building improvements
Property, Plant and Equipment
Property, plant and equipment, Gross	8,502,000	8,447,000
Machinery, equipment and tooling
Property, Plant and Equipment
Property, plant and equipment, Gross	15,544,000	15,503,000
Construction in progress
Property, Plant and Equipment
Property, plant and equipment, Gross	$ 162,000	$ 106,000