https://everyspec.com/MS-Specs/MS9/MS9200-9299/MS9201B_7846/
MS9201 B NUT PLAIN HEX BOSS CONNECTION CORROSION STEEL
Title: MS9201, Version: B, Date: 1976-Sep-30, Desc: NUT PLAIN HEX BOSS CONNECTION CORROSION RESISTANT STEEL (30 SEP 1986) [S/S BY SAE-AS9201]
bnutplainhexconnection