Electronic Sorting Marks

Between 1967 and 1983, Scottish £1 and £5 notes featured electronic sorting marks on their reverses (see here for an example). As far as I know, these are unique to Scotland but, if anyone else knows of any similar marks on other notes, could we please add a tag for these marks? If it's just Scotland, it isn't necessary but, if this was done elsewhere, it would be useful to link them.

There are a dozen of security features you might not or outright can't see but machines do. Like magnetic shapes, UV prints, hidden patterns etc. so I doubt these notes are unique in that sense. But you can always write something interesting in the comment-sections.

I don't think these were security features, rather they allowed machines to identify and sort the differenct denominations, like a bar code.