Hi there, I came across this note and noticed the small lettering on it, what would appear to be "MM1". I kept it to compare with a few others I've come across and have also checked online but not found anything else with these marks. The markings are only on one side and look as though they are part of the bill, not stamped on or anything else as such. All the watermarks etc seem to be legit on the bill. Is it likely this is some kind of printing error, or a particular serial number that has this marking, or just someone playing silly buggers? Just thought I'd ask here in case someone knows if it's worth looking into further. Cheers.