I am also looking at Middleburn. Whole thing was bought by BETD, https://www.bikerumor.com/2016/10/20...nk-brand-line/
They had RO1 (square taper) and RO2 (external bearing) for their road line. Their mtb and tandem models are very popular with good reputation in SS and mtb crowd.
To my knowledge original Middleburn was part of bigger company (aerospace and formula one).

I had a chance to test ride them once on my friend's bike (I think he had RS8), they felt very nice and machining/finish was exceptional. So if brand is truly resurrected I may get them