Hi Vandoo,
The area behind the singa, I presume you are referring to the picetan, is carved out as part of the perabots of the keris. It's not a thumb depression akin to those on keris picit.
There is a metal ball in the mouth, and it looks like it was painted in gold colour. Brass/copper paint probably; don't think there's any actual gold in the paint.
I think it is an old blade (>100yrs old, late 19th century) from E. Java, but I'm not sure. That's why I'm putting it up for discussion.

There are signs of pitting on the sor-soran area, especially at the outer edge of the 1st luk. There are some very tiny perforations on the sraweyan area that allows light to pass through, probably due to acid cleaning over the years. The rest of the blade has better surface condition, with some nicks here and there, and a few pits.
The blade is not too heavy, which tilts the opinion towards an old blade (the result of more thorough forging). Madura muda blades, I noticed, tend to be quite heavy. However, if you notice, the singa itself has a rather smooth surface. The eyes and other features of the singa looks a bit worn smooth, so I don't know if the singa was polished recently.
Old? New? Modifed? I seek fellow forumnite's opinions please?

Thanks.
But regardless, I like the piece a fair bit (not to mention the pelet wood). Just want to find out more about the piece.