As Jussi mentioned - yes, Bizen, yes - authentic (rarely (if at all) anyone would fake a signature of such piece And put a date on it), no - it is not mass produced sword (look at the overall quality of hada + hamon). Definitely worth sending for shiage (it might not even need that as there are no kizu or any issues whatsoever) just to bring out the hamon and hada better and then send it to be papered. Similar dated Sukesada wakizashi from the same era were advertised on Aoi website for about 5k. It is a good work made during war times when many blades had to be produced as the demand was high, however most were inferior to the standard and mostly unsigned or signed but by the pupils of the smith. Signed and dated works from those years usually (but not always) speak for 'special' order which gives me extra confidence of its authenticity.
J.