Dear Br.

Assalamu Alaykum wa Rahmatu Allahi wa Barakatuh,

Technically, it is not Riba because the coins have a transportation burden. They are the kind of Fulus in the past that many argued that they carry a burden in carrying them. But still I believe there is that nuance  (shubhah) of Riba because it is the same currency. If I were you, I would not collect that much and if it happens, I would consume them through purchase and through time.