What component is referred to by the nomenclature M170A1?

The nomenclature M170A1 identifies the lightweight bipod used for the 60mm mortar system. This is a critical component because it provides stability and support for the mortar when it is fired. The lightweight design is particularly advantageous for infantry units, as it allows for easier transport and quicker setup in the field. The bipod also facilitates accurate aiming and enhances the overall operational effectiveness of the mortar crew, enabling them to effectively engage targets with precision and speed.

In contrast, the other components mentioned, like the square baseplate or various types of round baseplates, are parts of the mortar system but do not align with the designation M170A1. The square baseplate refers to another type of stabilization system, while the round baseplates serve different functional needs based on size and application within mortar operations. Thus, the M170A1 designation specifically points to the lightweight bipod, making it the correct answer.