To me it looks like Persian wootz.
Why doesn't come out as in high contrast, I don't know as it can have many causes.
I found out the best etching results are on surfaces polished to 2500-3000 grit. Higher polish gets worse results as the etchant does not "bite" the surface.
I got best results with Nital 4% but this needs to be top quality etchant. I found out that some Nital suppliers don't respect the advertised concentreation and you don't get the expected results. Most of the times, I needed to apply Nital more times.
As for the last few years I wasn't able to get Nital anymore, I started experimenting with ferric chloride, in commercially available concentrations, then diluted but without any rigurous measuring. Got generally good results with ferric too.
I found out that even on the same blade there may be areas that display hugh contrast wootz pattern and some areas that won't display any pattern at all or a very faint one.
My guess is that if the blade is reheated it may loose partly or completely the wootz pattern. I suspect this may be the case of your blade.
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