Looks like the question has been answered by smarter people than me but here's a good quick summary:http://www.thesamura...ta_te_uchi.html
Bottom line, a katate-uchi essentially is an O-wakizashi (or barely past the arbitrary 2 shaku limit for a daito) 150 years or so before the definition of a wakizashi was formally enshrined in law by the Tokugawa Shogunate and decades before wearing a daisho was standard. It was intended as a "quick-draw" secondary offensive weapon for unmounted warriors but by the time of the Sengoku Jidai, trends and tactics favored the longer (2-handed ) katana over the katate-uchi. I think the so-called kazu uchi mono mass-produced blades were the "rank and file" swords of the Sengoku Jidai and they were like the OP's sword, only of much poorer quality.
This is just my own random guessing but this is also around the decades when metal plate armor showed up on the battlefield to counter matchlock guns; maybe 1-handed swords just weren't up to the task? Swords were of lessor importance on the battlefield anyway so it could have just been dictated byfashion.
Ultimately you'd have to define "katate uchi" by their short nagasa, sakisori, short nakago and having been made in that 1450-1530s time window, not to mention being mounted as one and not a wak/katana (just like how a tachi is only a tachi if you don't mount and wear it upside-down ) The concept didn't die though... instead it evolved into the shinogi zukri wakizashi as part of the daisho, so you could have the benefits of both a shorter 1-handed and longer 2-handed sword on your belt.
Hi Jason, I have a bit more time now, no fun trying sound sensible at 5am
You say a "katate-uchi" is essentially an O-wakizashi, hmm, I have one here with a 59cm nagasa, just as easy to call it a short katana
As for the 1450,s to 1530,s window, not too sure, this is a good read http://www.nihonto.c...rtsuebizen.html
I did say we over-catergorize stuff, but hey ho, here we go, take a look at no7 running into the Azuchi Momoyama 1573-1600 http://www.yamakawad...es in shape.pdf
Ive read on Aoi a few times (as an example), that no kazuuchimono where produced Eisho.
As mentioned before, look at the sword quality before the mei, look for quality original bo-hi in these swords.
As you say, katate uchi were no match for firearms (introduced 1542), they where an auxiliary weapon, but as an Ashigaru, you would be glad to have one, just in case your matchlock got wet or something