Hi David,
An interesting read may be found
here, in which the author (Kevin Jones) discusses at some length the different aspects of variability in the process of manufacturing. Notice that eight of the nine variants possess at least a yakiba if not a hamon (I would classify your example as the former). You might even consider reaching out to him directly.
An interesting note: according the article, after 1933 any non-traditional sword was to have been stamped on the nakago to indicate it were not gendaito. While there are plenty of indicators in your example that point towards a late-war production, the presence of a tang stamp does not appear to be one of them.
Hopefully Rich can shed some light as to whether this practice or standard had been eschewed by the time the late-war ersatz examples were produced?
Anyway, here are the nine variants as listed in the article:
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1. Tamahagane gendaito. Fully hand forged and differentially hardened in the traditional manner using water as a quenching agent. Possesses an active hamon and hada.
2. Mill-steel gendaito. Fully hand forged from mill steel or (more often) 19th century railway tracks made from Swedish steel. Differentially hardened in the traditional manner using water as a quenching agent. Possesses an active hamon and hada.
3. Koa-isshin Mantetsu-to. Made from Manchurian steel by a special process. Partly forged, partly engineered, and differentially hardened in the traditional manner using water as a quenching agent. Possesses an active hamon and hada.
4. Han-tanren abura yaki-ire-to. Partially forged from mill stock, some folding, differentially hardened using oil. Does have a hamon although it is nowhere near as active as a water-quenched sword, but lacks hada.
5. Sunobe abura yaki-ire-to. Drawn down, forged to shape, not folded. Differential hardened using oil, may have a fairly inactive hamon, but no hada.
6. Mantetsu-to. Rolled from Manchurian railway tracks. Differential hardening using oil, may have a fairly inactive hamon, but no hada.
7. Murata-to. Rolled or drawn, oil hardened but not differentially hardened.
Yakiba but no visible hamon and no hada.
8. Tai-sabi-ko. Stainless steel, oil-hardened, no grain, no hamon,
possible yakiba. Made for the Imperial Japanese Navy to resist salt corrosion.
9. Machine made. Serial number in the blade. No forging; stamped out and quenched in oil without differential hardening, assuming that they are hardened at all. No hada and no hamon. Some may in fact be plated, and in the worst cases the hamon may be acid etched onto the steel. The classic example is the NCO swords. On a par with Chinese fakes, and the most commonly faked sword.
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Lastly, I don't know if this has been mentioned already, but the gunto koshirae are a poor fit to the blade. I have a hard time imagining a habaki - even with a theoretical missing tsuba - would or could cover that much real estate...
In the end, more conflicting data, though my "gut" still leans towards a late-war production... I still think you will receive a more definitive answer over at the NMB. IMHO I would post it in the gunto forum and see what the members can tell you (this sets the bar at a level to either meet or exceed expectations).
Regards,
Chris