Condensed Income Statements (Unaudited) - USD ($)	3 Months Ended		9 Months Ended
	Jan. 31, 2025	Jan. 31, 2024	Jan. 31, 2025	Jan. 31, 2024
Income Statement [Abstract]
Net Sales	$ 4,912,000	$ 5,394,000	$ 16,306,000	$ 16,175,000
Less: Cost of Goods Sold	(2,614,000)	(2,734,000)	(8,349,000)	(8,145,000)
Gross Profit	2,298,000	2,660,000	7,957,000	8,030,000
Operating Expenses
General and Administrative	344,000	396,000	1,098,000	1,097,000
Sales	726,000	705,000	2,320,000	2,181,000
Engineering	32,000	41,000	86,000	78,000
Total Operating Expenses	1,102,000	1,142,000	3,504,000	3,356,000
Income From Operations	1,196,000	1,518,000	4,453,000	4,674,000
Other Income (Expense)
Other	1,000	32,000	97,000	41,000
Dividend and Interest Income	536,000	396,000	1,152,000	855,000
Unrealized Gain on equity securities	92,000	2,883,000	1,505,000	2,149,000
Gain (Loss) on Sale of Investments	341,000	18,000	890,000	(55,000)
Gain on Solar Tax Credit	95,000		468,000
Gain (Loss) on Sale of Assets			(2,000)	8,000
Total Other Income	1,065,000	3,329,000	4,110,000	2,998,000
Income Before Provisions for Income Taxes	2,261,000	4,847,000	8,563,000	7,672,000
Provisions for Income Taxes:
Current Expense	602,000	474,000	1,771,000	1,327,000
Deferred Tax Expense	52,000	1,134,000	264,000	787,000
Total Income Tax Expense	654,000	1,608,000	2,035,000	2,114,000
Net Income	$ 1,607,000	$ 3,239,000	$ 6,528,000	$ 5,558,000
Income Per Share of Common Stock
Basic	$ 0.33	$ 0.66	$ 1.33	$ 1.13
Diluted	$ 0.33	$ 0.66	$ 1.33	$ 1.13
Weighted Average Number of Common Shares Outstanding
Basic	4,895,382	4,899,692	4,896,281	4,918,746
Diluted	4,915,882	4,920,192	4,916,781	4,939,246