Robert , I was the buyer of this sword and thought you would be interested to know how it turned out.
The late Robert Lewert had a Juyo blade by Bishu Suyetsugu that was dated 1378 . This featured in the May 1974 JSSUS Newsletter . The length and shape of Lewerts sword are very similar to the one that I purchased . In the translation of the Juyo write up that is in the Newsletter the shape is described as " Naoshi Nagamaki , shobu zukuri, high shinogi " I think that it is fair to say that the shape of the ebay sword was also Naoshi Nagamaki.
I took a punt on the sword for two reasons . Firstly the mount was in my opinion the best Katana mount that I can recall seeing on ebay for ages .There are lots of mounts with mediocre fittings that come up but I thought this one had some class about it . The Fuchi Kashira were good , tsuba by Owari Sadahiro , fine silver foil habaki and gold foil seppa . As a generalization you would expect a mount of this class to have an OK blade in it . Secondly the blade was Nagamaki Naoshi and as you said, seemed to be about 70 cm long.The very few blades of this style that I have seen in books or in the flesh all seem to be attributed to or be by Nambokucho smiths so I thought that there must be a reasonable prospect that this blade was too.
When it did turn up the mount was as classy as I had hoped for. The blade is 68 cm long and is in fair condition . The hamon is nioi based and I would decribe it as undulating suguha with some Ko midare and ashi . There are a couple of rounded spots in one area of thi Ji which might be shintetsu . I think I have got myself a probable cut down Nambokucho Nagamaki . There is a shinsa out here in September and I will put the blade in that and see what the experts think !
Ian B