These Vintage Genuine Issue crimping tools from the 1960s were used for splicing WD-1 and other telephone field wires. They come with an OD green canvas bag with a main compartment, and two smaller pockets for small tools/wires bag has printed on the front with black letters (MK-356/G). They make a great collectible tool. 

These GI Wire Splicing/Crimping Tool are used, although the condition is very good, they might still show signs of moderate wear and age.

• Heavy Duty Iron
• Canvas pouch MK-356/G
• Measures 12 ¾ " when closed
• For splicing WD-1 and other telephone field wires
• Pliers type handles
• Made in the USA
• NSN# 5120-00-679-2380

Crimpers are tools used to make cold weld joints between two wires or a wire and a connector, such as lugs. Ideally, the electrical and mechanical properties of the weld joint are as strong as the parent materials.