File or vise?
May I suggest that you look at this pattern under magnification, Lew.
There are criss-cross lines with a diamond between.
If the lines are impressed and the diamond higher than the lines, I think we are looking at a file.
If the diamond is impressed and the lines are higher than the diamond, I think we are looking at a vise imprint.
Have a look at the jaws on a metalworking vise and you'll see what I mean.
Regarding the different colour and texture of the edges.
A keris blade is not normally tempered. It is taken to critical, and then quenched to harden it. The tempering that reduces the hardness of a blade to minimise risk of fracture is not normally done with a keris blade.
However, there is another way to minimise risk of fracture, and that is to ensure that only the point and the edges go to critical, whilst the center of the blade stays below critical. This is not such a big trick to do, if you harden by passing the blade through a live flame, and quench as soon as the edges get to critical, which of course is going to happen a lot sooner than the center getting to critical, because the edges and point are thinner.The result is that only the edges have undergone the structural change that makes steel hard, and only those edges are going show the characteristic darkness, and long term erosion associated with hardened steel.
Result:- hard edges, softer center; a similar result to what would have been achieved if one had drawn.
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