Actually, it doesn't. The trade shows were end-of-year events and the catalogue supplement 17a was published in 1978.
Are you really sure your Guerciotti was built in '77? If you can trace the intro of Portacatena to early enough in 1977 for a builder to use it on a production bike, you should let Chuck Schmidt at Velo-Retro and the folks at Tutto Campy know so they can update their Campy timelines.