Not smartstamp, but what?
It is not a normal old fashioned franking machine as it contains a barcode.
It has Royal Mail logo but not the usual second class mark.
It has an IEC16022 datamatrix barcode like a smartstamp, but a different geometry variant. The content are a very similar style to a smartstamp, and include date and price and so on.
I assume it is some sort of franking system - but what?
Update: Wow, after all of the hassle we had trying to get a spec for smartstamps, it seems MailMark is a system that RoyalMail allow systems integrators to work with to make mailing solutions. They have a process for becoming a producer. I think we may have to look in to it - to replace our use of smartstamp and make a sellable system!