The plant characteristics are all wrong for it to be a Tolumnia.
Here's a pic of a typical Tolumnia. Also these do not look like 'thin' roots to me. They're thicker which along with the aparent lack of pseudobulbs would rule out Oncidiums. It's roots are epiphytic which rules out the semi-terrestrials like Phrags. Now having said what's it's not, i haven't a clue as to what it is. I've toyed with the idea it is a Zygo of some type but again...no pseudobulbs....