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There is a lot of collaboration or simply making a living for some famous smiths.
eg Tsukasa makes machetes for Ajigataya.

I even have a Kai cutlery paring knife with Shigefusa stamped on it.

If they're fakes the faker must be a lousy businessman. Why not add the tamahagane stamp rather than sell them as Swedish steel ? More money in folded steel.

Some of the Swedish steel ones have the double stabiliser.

http://straightrazorpalace.com/auction-talk-ebay-etc/132480-unmarked-iwasaki-razors-ebay.html#post1740988
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