[Gustav]

For Cengkrong and Cundrik the normal position in the sheath is reversed, because reversed is the Gonjo, not the hilt.

The general problem is, as I understand it, that Marco's Keris isn't Cundrik or Cengkrong.

Well, one of Pusaka of the Empu lineage from Magetan is a Pedang-like Keris, which isn't Cundrik or Cengkrong, because it has completely different Ricikan, with reversed, quite unconventional Gonjo. So the position of it in the sheath is reversed. It is traditionally dated back to the first Empu in Magetan lineage.

What I also understand is, that Marco's Keris is a more like a Dhapur, which normally sits in the sheath the common way.