Hello,
I posted this portrait of a samurai taken in Yokohama in 1881 over at /r/ColorizedHistory. Whilst I'm confident the colours are accurate based on the original hand coloured print, one of the commenters asked what the hinged door in the cuirass was used for, and I honestly don't know.
Given the distinct pinching of the cuirass itself, this particular variant of armour appears to be a Hatomune dou (dō) gusoku (pigeon-breast cuirass), and the hinged door can be clearly seen.
If anyone out there has a good working knowledge of samurai armour can tell me, I'd be most grateful. It may even be possible to identify this warrior's clan by the mon.
Thank you!
It is rare that I wander outside the boundaries of my medieval Europe flair in /r/AskHistorians, but long ago I had a certain passion for samurai armour (because of beauties like this). The hinged hatch/door is very rarely seen, but has been found in earlier century costume on the side and later in the front of the Do (cuirass). I've encountered three 'explanations' for it: document storage, battlefield medicine storage, and a hatch for airing out the torso. Frankly there isn't much space in there for anything else, and it's not easily accessible. I'm not much convinced by the seppuku suggestion by /u/JarHeadVet : it doesn't fit the ritualized manner of this form of suicide to just 'open the hatch and stick in the knife'; it also overlooks the fact that the hatch is found in places that have nothing to do with seppuku.
It is rare enough that the some have suggested that a hatch was simply an idiosyncratic choice by each armorer, made bespoke to a wearer's individual request and for reasons now lost to us.
if you look at the japanese armor shown here, at least two of these specimens have similar shaped and positioned flaps that are described as storage pockets:
http://elogedelart.canalblog.com/archives/2009/10/25/15564222.html
