What happened with this blade?

[Sajen]

Originally Posted by A. G. Maisey

Detlef, I suggest that you take this blade into very good light, and closely examine the apparent patches under magnification.

That would be where I would start.

On the side of the blade opposite to the apparent patch, I am assuming that there will be one of the pools of pamor which form the pamor motif. If this is so, the indentation that caused that pool of pamor may have been taken a bit too deep during the manufacture process, and with time the iron covering has eroded and exposed nickel from the other side of the blade.

Yes, the colour of the apparent patch seems to be brighter than the other contrasting material, but it seems to me that at least one layer of the contrasting material is also a brighter colour, it looks like there are flecks of brighter colour contrasting material along the blade.

Alan,

thank you very much for comment, I have hoped that you will do so since I think that you have the best knowledge of forging technic and when someone will know what happened with this blade it will be you.
I have looked many times already by good light and with magnification to this point of the blade and are still unsure. You are correct, on the opposite of the blade is one of the pools and first I have thought that it come through but there is a little space between the iron and this "nickel" (I think that it is nickel). I have tried to take some better pictures to show it. But I will take pictures again by daylight to show the very different colour.

Regards,

Detlef