Saw this here. 

History: The Handy Twine Knife

The Handy Twine Knife was invented in the late 19th century by James Caldwell, an innovative postal worker looking for a more efficient tool to work with the twine-wrapped bundles of mail. Mr. Caldwell ran a train route from Pittsburgh to Chicago, in an era where postal workers carried sidearms (to fend of train robbers). Deciding his pocket knife to be inconvenient for repeated use on a moving train, he decided to invent his own solution in the Handy Twine Knife.

Working 4 days on / 3 days off, he started making the knives in his downtime to sell to coworkers. The knives caught on and became standard issue for many postal workers across several decades. Despite the USPS being the first and largest customer of the Handy Twine Knife, they eventually stopped ordering them due in part to unfounded concerns that the knife could be used as a weapon. To this day, the HTK is used widely in all types of manufacturing and processing. 

Product Specs:
Manufactured in Upper Sandusky, Ohio for more than 100 years
Aluminum ring, steel blade
Titanium Nitride coating on the blades for extended sharpness and durability
Available in 3 sizes, ring sizes 9 (small), 12 (medium), and 15 (large)
Completely food safe