Herter's had a large store in Beaver Dam, Wisconsin, the main outlet in Waseca, Minnesota. The .401 was called the ".401 Powermag", and as far as I know, only Herter's had a revolver chambered for it. They were inexpensive but a well-made piece. Finish was a little rough, but at the price they were good value. Performance was not in the .44 mag class, even though Herter's implied that it could be. A friend of mine owned two of these pieces, bought them around 1963, and handloaded to about equal today's .41 mag specs. Whether or not he was pushing things a little I don't know. He never experienced any weapon failure. If you can find an old Herter's catalog (1963, 1964 or thereabouts) at a gun show, get it. It's quite a reading experience. When this company went under, a lot of grown men cried.
DC