I don't think steve is an MBK. I think he's got some VERY strong Baja influence there. I think the species is conjucta, but am not positive and don't have a field guide handy.
I've never seen a full blooded nigritis with any kind of striping at all.
I have produced a few of them, though not for a while.
When I went to the vet he told me it was a MBK. He said they can vary in colors and patterns too, so I'm just going to go with MBK until I find out what he really is.