Invention infringement has been around longer than maybe we thought we knew! The TV show Museum Secrets aired an episode that featured a Viking sword. The Ulfberht sword brand (between 850 to 1100 AD) was said to be the strongest in its day yet the majority unearthed in modern times found were in pieces. Apparently the well know indestructible sword know to fetch a good dollar with the name  ‘Ulfberht’ branding on the blade, was often knocked-off by other smiths and passed off to their viking customers as the real thing.