Daniel, If I'm not mistaken, National and Timken are parts/subsidiaries of the same company. For Instance, I bought a Timken seal awhile back and it had "National" stamped on it. I know they do make their parts here in the states and in the asian market. So, it's a toss up where they are actually coming from. TImken has really good quality standards, so I wouldn't be afraid of using anything they make.
Chris