This model was Apple®'s first portable Macintosh® and among the first commercial computers to use an active matrix liquid crystal display, which provided greatly improved contrast and reduced response time at substantial cost. This model (although not this specific unit) has the distinction of having been the first commercial portable computer used in space and the first to send email in space (Space Shuttle mission STS-43, 1991).
This item clearly marked as being a pre-production prototype. While the accompanying property pass is dated after the Portable's release (September 1989), the transfer is marked as 'permanent,' suggesting it was used within Apple during the development process and given to the employee after the machine went into production.