Ma Bell seems like a good guess. It could be another cross malipoensis and brachy (like Paphiopedilum Christiana Richards), but those don't see that common. I would go with Ma Bell.
As we are trotting the dark paths of intersectional hybrids, I'm sorry, I fear I cannot be of much help to you, Per. But with that proviso: P. Ma Belle doesn't seem totally of the mark!
There is no way to tell what it is for sure as all these malipoense x brachy turn out pretty much the same. Malipoense x brachy is about as far as one can go for sure when it comes to its ID.
Most Ma Belles I have seen and those in the awards and Wiz show the longitudinal markings (on petal bases) of malipoense (we call it reticulations in judging). This one doesn't display this trait. But that doesn't rule out the possibility of MB.
Like most above, I do agree it is a malipoense hybrid (due to the deep maroon marking on the staminode) with a brachy of sorts, possibly not even a primary hybrid (see pics of Mem. Margarite Ringler).