I have the exact same stem and tried to work out what brand it was last year so I could find another to buy. Somehow I concluded it was most likely Hsin Lung, a Taiwanese parts maker, but wasn't able to track any down online. Looking at it again it looks more like 'NJ'.
BTW badger_biker, great looking bike. I'm curious how that front STI shifts with that Deore crankset. Did you use a mtb or road FD?