I say lopi cardigan, although this one isn’t in lopi. But it’s a lopi pattern and the closest thing to the “real deal” possible for the intended wearer. The front bands are knit, in seed stitch and sewn to the body. There are nine sts in each band, six for the band it self and three to cover the steek on the reverse side.
They are sewn with Kitchener stitch (grafting). First you stitch into the band, just after the third sts, and then the same way on the body,
right beside the knit sts. When done on the front, you turn the work and hide the steekwith the three sts wide band, that is now on the wrong side, in the same way:
I like this method, it’s very neat, and not hard, although it’s a bit time consuming.
My Lopi Cardigan “Career”
Most lopi cardigans I have done, have crocheted button bands. These three are almost identical:
This one has not only crocheted button bands, but also homemade glitter buttons. It’s not steeked, it was worked flat:
This one has crocheted bands, and a zipper:
but this one has buttons (obviously)
So do these :
This one has knit bands and a zipper:
and this one has an inserted zipper and no front bands at all. 
And finally, this one has wide ribbed front bands. This one was worked flat, on very fine needles:
