No. . . sorry, if the answer had been as easy as a Dash 7, C-27 or
C-123, I wouldn't have bothered you guys. I remember pictures of a
prototype flying, but I am certain it never went into production.

It was a high wing four-engine turbo-prop with a very square or
rectangular fuselage cross section. It was developed in the mid to
late sixties or the very early seventies. I seem to remember it was
being initially developed in the U.S., with production possibly in
Puerto Rico.

Thanks to all for the thoughts on the subject. Blue skies

John