Neat one! Very unusual... Could be a weird mutation of nobile, but might also have some genes from another species.
Based on the look of the pseudobulbs, it could have some ancestry from a species like findlayanum, pendulum, falconeri, or wardianum. Such swollen nodes on the PBs aren't typical of nobile (at least not on any I've seen in cultivation, populations in Australia and elsewhere certainly might have different genetics).
My guess is that you may have a primary hybrid of nobile and wardianum (registered in 1888 as Den. Murrhiniacum, according to the RHS, and I think also existing as a natural hybrid, Den. x murrhiniacum) or something derived from that cross. Based on pictures and descriptions, Den. wardianum has swollen nodes and twisted flower segments that might produce the odd shape of the blooms on yours.
Than again, you might have a natural hybrid, like a nobile with wardianum ancestry a couple of generations back because of a range overlap, or who knows what... Just my

(and a bunch of guessing!), and probably wrong...
Good luck!
--Nat