Ink On Notes

It may depend on the country. In the US you can turn in pretty mangled bill and it will be accepted. I know in Russia many people were hoarding $US (before Euros overpowered) because of instability of the local currency. There it was hard to move bills that were less than perfect. But I don't believe you'd have a problem at a So.African bank with a stained bill.

OK, here is one other possibility. The banks here in the states, use "red or purple die packs" that they drop into the bag / container whatever the "bank robbers" use as their portable method during their get away. The "die packs" in return explode after a few seconds thus creating a stain on the note. Apparently this stain if one is to get it on their hand is not easily removable and is used for the authorities to track down the robber.

I have seen similar stains on notes here in the states when I search through notes. I am in no way implying your note had a similar fate in the past and am just throwing out a possibility.

To circle back to your ? As long as both serial numbers are visible all banks have to accept it by LAW here in the states.

Peace