As I know it here in Java, this kind of pamor in blumbangan called 'tlaga membeng'. "Tlaga" means lake, (much bigger than "blumbang"= pond/fishing pond), "membeng" is rippling water, the effect you get if you throw a stone in the middle of a lake/pond.
It is a very positive pamor. Some are intentionally made, as Marco's, and some aren't. Those who aren't usually came in Beras Wutah or Pedharingan Kebak pamor.
On Marco's keris, it's made by the precise cutting of blumbangan through the wengkon line. It also need a precise forging so the wengkon line laid where it should.
The best I've seen is a keris with Adeg Wengkon and Tlaga Membeng. Black and shining iron, grey-greenish edge/steel, sharp, white pamor. A pamor lines on each side of ganja. As perfect as if you draw it with a scriber.
Simple pamor, but not simple to make.
No, I don't make up the term 'Tlaga Membeng' if ones wondering
