Shail,
Just for the start, BRINKS bought one unique Signature DNA. IMO, they will buy few more. Lets say they use this first mark to protect cash, once the ink is over they need to buy new one. It was not mentioned if they mark in house or by third party.If they get training then they will mark inside so that will be recurring revenue.
Sometimes, this 50k recurring fee is profitable for APDN sometimes it is not.