Jnat Question - Where are These From?

For those of you who have seen a lot of Jnats, I have question regarding a type of stone that I seem to see and get quite often.

A picture of one is here:

https://postimg.org/image/7vawnv205/

I may abuse terms here, because I'm not exactly a kanji-phile, but they look like light green (but not nakayama light green) hones and they are very fine, but once they break in, they become superbly fine. At the same time, they are very smooth feeling and with very little cutting power settled in well, so folks desiring the fast kiita type wouldn't think much of them.

I like them, but have no clue what they are. I seem to find them in bench stone and barber hone a lot when I buy a blob of stones.

Any clue what mine they come from? There's no skin on any of them on the back, at least not something notable like you'd see on a nakayama stone or an okudo suita or something where the skin on the back is very distinct.

A picture of the razor edge from one (the tomo in this case was fairly aggressive, still fine, and the scratches at the very edge are probably the result of strop contamination). the edge is extremely uniform from this stone, I think due to its lack of cutting power - if you finish the edge with the tomo, anything you do after that is relatively harmless.

https://postimg.org/image/v0lb9v751/

Unfortunately, this razor is soft and not able to hold this edge for more than half a shave - and that softness might have something to do with why it doesn't look a little bit better (why the scratching on the bevel is so prominent despite such a nice edge). I confirmed the same with a second stone - the razor is junk, a NOS boker tree brand razor that's really pretty with three pin scales, a super fine grind, but junk nonetheless and will probably be repurposed as a shop knife of some sort.

If it helps with the mystery, all of these stones are old antique picked stones, and not newly cut or newly stamped stones being sold by a distributor.

I won't be offended, by the way, if someone says "I don't think those are main mountain stones and they look like junk" (or are junk). I kind of like the two that I have. They're really slow, almost like a super PHIG - slightly faster than that, but gentle like a good phig on water with lots of control.

I'm assuming the very slow speed on clear water is a suggestion that they're a low-quality stone. Narutaki can sometimes have that reputation, but narutaki stones often look a lot more like nakayama.

There's not a lot to go on in the image, color does not usually mean much as far as mine origins go. Alex Gilmore has said that the ring pattern was typical of Nakayama and Narutaki, so I would guess one of those.

Cheers, Steve