So I picked up a few roll of expired (01/2006) Gekko MW 400 Plus. I can't seem to find all that much info on the 400 ISO version of this film. All I got to go on is that the film was made in Europe for Mitsubishi and that it comes in a clear plastic container with a red lid.
Remembering slightly vaguely . . . didn't Mitsubishi take over the remains of Konikoshiroku (spelt wrong probably, but they traded as Konica) ? Konica had an agreement in the past with Ilford to provide C41 colour film under the Ilford label. That was nearly thirty-five years ago though oops, hmmmm, perhaps your film is not evidence of a bi-directional labelling exercise after all.
I meant that Ilford sold Konica-produced C41 film (I know because I bought lots of it), labelled as Ilford - so possibly there was black-and-white film provided to Konica, if the brand did indeed end up with Mitsubishi. But the dates don't match up, though the rolls found by the OP were probably made before the Ilford buy-out, so maybe?
Not konica Due to being made in europe. Yes Mitsubishi color film from the same time as this film is konica made. But this b&w film is not konica stock