hi mikee
this was a great help to find this sword smiths name they know thier swords as i can not read japanese but i have hawleys books on all the sword smiths of japan that i looked up i believe i found your smith if im reading it properly there is about five pages of masa hiros with all different years so i was right about on target with your 1600s made blade i found on page 329 entry number mas-173 in hawleys book this smith reads like above kawachi daijo fujiwara masa hiro if im correct this smith is a 50pt smith blade dates from 1658-88 thats a good smith that did extra work to the blade they didnt give him 50pts for crapy work so all in all i believe i might have found your man check back with these experts and see what they have to say about hawleys book information hope i have helped you and yes you have a real original old koto japanese sword blade no if but or ands its the real deal might be worth a polish and fixing please let me know what they say god bless merry christmas andy militarynut