I suspect it was new old stock and had been sitting gathering dust for
35 years or so before you came along.
Details of the box (if you still have it) might help confirm this.
Currently the 364 model, which uses the same basic body and covers as
the Marine Band Soloist, comes in a dark red plastic wraparound pouch.
For awhile in the 1970s they came in a bright red pull-apart tube-like
box with left and right halves. Before that they came in the classic
lidded paper box, with the later ones having that cheery blue Hohner
logo and the earlier ones having black and gold medallion labels on
the
inside boxtop and possibly on the bottom.
I don't know what sort of box the Soloist came in, but there may have
been a similar progression in the type and the appearance of the box.
Winslow