Hi Jim,
The easy way to tell without blooming it is to rip off one of the p-bulbs and cut it in half. If hollow, Schom or Myrc. If not, Dendrobium.
My gut reaction when I first saw it was lindleyi but the p-bulbs on lindleyi are much smaller. So then I thought jenkinsii, which it could be (same Den section, closely related). But I know it is Dendrobium.
The Schoms and Myrcs only bloom at the apex in the center of the bifoliate leaves. If you look really close at the top of the p-bulb, you can see the old bloom nodes on the side.
So my money is on Dendrobium. (I'll post a photo of a dissected Myrc as I have 4 of the species in my collection).
