Hi trvrhldr, as indicated in the descriptions of the coins, KM#47 has a reeded edge and KM#47a has a smooth edge. In addition, the size of Jose's head is slightly larger on KM#47a (on the whole, the portrait on KM#47a looks a bit 'clumsier' than on KM#47).
One might argue whether this justifies two KM-numbers, but that's apparently what K&M decided upon.
It's probably the material difference. Magnet test should be the easiest way to check (of course if the edges are different it makes the checking even easier).
Come to think of it, Russian 10 and 50 kopek 2006 also come in a magnetic smooth edge variety and a non-magnetic reeded edge variety. (And the rubles from 2009 are just magnetic and non-magnetic, without even the edge difference.) Yet I've never heard of anyone complaining of being unable to tell one from the other.
Photos can be unhelpful in cases like that (the pictures for the magnetic and non-magnetic types of Kiribati 5 cents 1979 are still the exact same coin).