Cast Iron Bowl or Pot, Enameled Inside, Marked

This may have been part of Leonard's hoard, but I'm unsure...it looks Japanese to me.
~6 1/4" rim diameter, 2 1/2" rim height, 3 1/4" to the top of the bail-mounts; wall thickness at rim is ~0.150". Weight is ~30 oz.

The interior is evenly covered in a high-gloss black enamel (glass), including the bail mounts, an' the iron had been very smoothly finished before its application, judging by the as-cast condition of the exterior, which is painted black. The three feet are worn to iron, but elsewhere there is evidence of incidental paint loss. It's hard for me to age Asian iron castings...they've been foundry-masters for a very long time.
Google image translates the upper right pair of characters as "south street chibu", without comment on the lower left pair. Are any of you able to illuminate that mark? I will be glad to know what this object was intended to be used for...an' when it was made, if that can be determined.
It just occurs to me that the iron alloy and/or the enamel ingredients may have been carefully chosen so their expansion when heated were fairly equal; the pot was perhaps made to be used in food preparation over heat, or in an oven. Any an' all of your comments are most welcome...Thanks for lookin'!

 

Looks like Japanese Nambu Ironware!
Mikey

 

interesting bowl..... the feet are so delicate !

 

Agree, it is Nambu Ironware. The black lacquer on the inside is also classic Nambu. I believe they included tea leaves in the lacquer mixture.

 

Very subtle. Very Japanese. They know a thing or two about design. Or three.

 

I'm puzzled by your use of the word lacquer for the glossy material lining the interior, AJ...'tho I profess no comparable expertise, I'm convinced the lining is enamel due to the conchoidal microchipping around both bail holes...I've never seen such fractures on any lacquer surface or edge.
I'll try to get a couple pics of those holes that show what I mean.
I respect your skills, an' don't offer this contradiction lightly.

 

Yes, it is enamel, that is what I meant.
My aphasia is playing up again, have been having trouble finding words. Even worse when I speak.

 

No Blame, AJ...we're all in the same boat, now or later!