Clare, the following document explains some of the basics of banana cultivar identification:
http://bananas.bioversityinternation...s/synonyms.pdf
But as Gabe regularly points out, it's not all that easy with about 1000 cultivars out there, many misidentified, different growth habitats under different conditions, etc.
In this case, the fact that the plant came from a source in the US and the bunch structure is "lax" (not tightly spaced fingers and hands), points with pretty high certainty to Orinoco.