There are three separate "Heritage Bank" organizations listed on Wikipedia: one in Australia, one in Ohio and Kentucky, and one in Nigeria.
I think we can rule out the Australian one, since Australian banks don't use chopmarks on foreign currency.
If it's a chopmark, then it's the Nigerian one. If it's overflow from a mis-applied bank strap, then it's the Kentucky one.
I'm leaning towards that last one, simply because of the "missing bit" at the bottom. Plus, this note doesn't seem to have seen much service in Nigeria; paper money doesn't stay this pristine for long in tropical countries due to the adverse climate.
Don't say "infinitely" when you mean "very"; otherwise, you'll have no word left when you want to talk about something really infinite. - C. S. Lewis