I recently acquired a sword signed "Echizen-ju TAKAHISA-saku" My dealer (Tokugawa art, Yuji Fukuoka) believes and I agree it is early Edo...most likely Genna.

However, according to Nihonto Meikan....
(There are two entries for Takahisa. One says " Echizen Kuni ju Takahisa" "around Tenwa, Echizen", the second says "Takahisa Echizen ju Fujiwara" (which seems very odd as it is the reverse of normal), "around Genroku, Echizen".)

However according to my dealer....