ASTM A240 / ASME SA-240 is the American standard for stainless plate, sheet and strip for pressure vessels and general use. EN 10088-2 covers sheet, plate and strip for general purposes in Europe; EN 10028-7 covers pressure purposes. JIS G4304 (hot rolled) and G4305 (cold rolled) are the Japanese standards; GB/T 3280 and 4237 are Chinese.
Grade names differ: 304 = 1.4301 = SUS304 = 06Cr19Ni10; 316L = 1.4404 = SUS316L = 022Cr17Ni12Mo2; 2205 = 1.4462 = S32205. A quotation should state the standard and the grade in that standard's naming.
Equivalence is close but not exact; nitrogen and molybdenum limits in particular differ between EN and ASTM versions of the same grade. For pressure work, specify one standard and stick to it.