My apologies to all for the meager sampling I have to offer as opposed to Merwyn's excellent work, but here are a few more.

The front of the Samurai AF gear


Lord Zuiko's statue

I like this one because it seems to verify what Merwyn pointed out above. The lefthand line on this sign seems to read "ZU I KO U"

And another example of the character for Doma, this one taken from within House of the Fierce


You can also see the Doma symbol in a few other places, such as on Gosetsu's robes (central back mon position, where usually a family crest goes). It also appears in a few other places but that's the first one that comes to mind.