There are many ways to make a blade look older, one common way is to leave the blade in acid for long periods of time. Sometimes, the blade is buried for a while. All of these artificial aging process has one common consequence -- the corrosion on the blade is too even.
Wear and tear on a keris blade that has taken place naturally is a 'random' affair, meaning that the rust takes hold on a few spots only. When cleaned off, it leaves a corroded spot while the other spots are not so corroded. Over long periods of time, this 'uneven' corrosion becomes more and more evident. Plus, natural corrosion of the blade by rust is also accompanied by constant rubbing of blade against sheath when it is put in and taken out of the sheath, so the blade surface while corroded, is smoothened out and has a 'not so sharp' surface. Artificially aged kerises, especially those with pamor miring, has a 'sharp' surface. Looking at the blade above, it is easy to see the superb evenness of the corrosion.
As for the blade having no slorok, you can see in spots of the blade where there is a gap between the pamor lines, but there appears to be no metal underneath. This is not the 1st time I've seen such a kind of blade with no slorok. The other example I've seen actually seemed to be of Riau or Peninsula origins as the pamor is of the non-contrasting form, and the dapur is also quite un-Javanese or Madurese. But then again, these kerises are meant to be 'lookers' and its not surprising that the modern day smiths take shortcuts to produce better-looking pieces faster.
At the end of the day, its what we are looking for as a collector that determines whether we should buy a keris or not, but we should buy it with our eyes open.
And as to the question of good kerises, it is recommended to read the "What makes a good keris" thread, but it is also true that 'good' is a relative term. When the market is flooded with poorly-made new pieces, the slightly better average pieces would look much better in comparison. While there are good old examples in museums (sometimes museums display questionable and not so good kerises too) and books for reference, they are usually forgotten because we don't see them every day, and there is a sense that those are kerises of a different level and not for the common collector. And so the 'good' applied to the kerises (including all the thousands of Madura Muda pieces) floating in the present world is of a different standard.
Anyway, enough of my ramblings, but just to show why I have faith in these Madurese smiths -- here's my example of a Madura Muda keris with pamor blarak ngirid, made properly with a slorok, and not artificially aged. Think many of you have seen this before.