CONDENSED STATEMENTS OF OPERATIONS AND COMPREHENSIVE INCOME (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Income Statement [Abstract]
Net sales	$ 7,240	$ 6,916
Cost of sales	4,460	4,189
Gross profit	2,780	2,727
Operating (income) expenses:
Selling expenses	142	33
General and administrative expenses	663	565
Gain on disposal of equipment		(7)
Research and development costs	484	408
Total operating expenses	1,289	999
Operating income	1,491	1,728
Other income (expense):
Interest and miscellaneous income	35	74
Interest expense	(59)	(20)
Total other income (expense)	(24)	54
Income before income taxes	1,467	1,782
Provision for income taxes	363	433
Net income	1,104	1,349
Other comprehensive income (loss), net of tax:
Unrealized gain (loss) from marketable equity investments, net of taxes	(57)	298
Comprehensive income	$ 1,047	$ 1,647
Basic and diluted income per share:
Basic net income per share	$ 0.28	$ 0.31
Diluted net income per share	$ 0.27	$ 0.31
Weighted average common shares outstanding:
Basic	4,008,017	4,330,636
Diluted	4,110,414	4,372,893
Common shares outstanding	3,990,995	4,249,548