I received this plant as a cutting from Ric Morier in the summer of 2014, and it flowered in January.  I can tell you very little about this Hoya other than it is very similar to Hoya pachyclada.  Here is a comparison photo between the two flowers:

Hoya pachyclada on the Left and Hoya sp. EPC-620 on the Right

The corona lobes of Hoya sp. EPC-620 seem to be more pointed than those on Hoya pachyclada, but other than that they are very similar.

Hoya sp. EPC-620 is fragrant; a quick grower, and belongs in every Hoya enthusiasts collection.  Its growing requirements are very similar to Hoya pachyclada in that it likes to thoroughly dry out between waterings.