All of these washers are produced in the U.S.A. Depending on the size, they are stamped or machined.
300 Series Stainless Steel
Tolerances:
ID and OD are +/-.010
Thickness Tolerance varies by size:
Up to 1/8" thick +.005/-.014
From 1/8 to 9/32" thick +.005/-.020
Flat and Parallel to within 0.005"