Yep, you're right, it's tamahagane. Sounded right at the time, but then again I couldn't remember Muramasa's name either.
Apparently some consider Japanese steel inferior due to after the War, Japanese smiths in Seki City were importing Swedish steel to use in their blades. This was due to much of Japan's mining industry infrastructure having been destroyed by US bombing, and also that the tamahagane has a naturally high amount of silica in it. Swedish steel billets needed no further refining and thus were more cost and time effective in a Japanese economy struggling to get back on it's feet.
Bugei, the company I like to purchase my stuff from, was at one time making their swords with scrapped rail road ties from Manchuria. Makes perfect sense! Manchuria has a pretty steep difference in tempurature (severe winters and damn hot summers) so you've got good tempurate tempering combined with tons and tons of train providing compression to the iron! I think I'd take that over traditional tamahagane.