Property, Plant and Equipment - Summary of property, plant and equipment (Details) - USD ($)	Mar. 31, 2023	Dec. 31, 2022
Property, Plant and Equipment
Property, plant and equipment, Gross	$ 34,132,000	$ 33,694,000
Less accumulated depreciation and amortization	(23,342,000)	(23,038,000)
Property, plant and equipment, net	10,790,000	10,656,000
Land
Property, Plant and Equipment
Property, plant and equipment, Gross	7,000	7,000
Buildings
Property, Plant and Equipment
Property, plant and equipment, Gross	11,886,000	11,843,000
Machinery, equipment and tooling
Property, Plant and Equipment
Property, plant and equipment, Gross	21,216,000	20,757,000
Construction in progress
Property, Plant and Equipment
Property, plant and equipment, Gross	$ 1,023,000	$ 1,087,000