Thanks Barry,
I was uncertain about the 'stories' of native manufacture .... the Japanese had limited supplies of 'raw' materials during the later stages of the war ....which may or may not have caused situations whereby blades were produced by 'local' techniques/materials. Many of the regions that produced Dha/Darb were occupied by the Japanese, and a lot of these blades were of very good quality.
Many of the later produced Japanese swords were of poor quality and not traditionally made....mono steel, oil quenched, machine made etc. So perhaps there may have been a few isolated cases of 'native produced' katana blades
As to 'Island swords' ....I only found one reference in a forum .....but no where else....so perhaps a Chinese fakers sales term to help sell their wares
All the best
David