Crimper type pliers

[HowardPgh]

What is this Bell System B tool used for?

[RotarDad]

I use mine for crimping spade lugs - they work well for that purpose, but are a little hard to operate since the handles open so wide.  However the the leverage gained makes crimping pretty easy.

[Whitcrane76]

They were used to crimp copper splice sleeves on open wire.
Here's an NOS pair with the factory test crimps still attached.

[AT2796]

The "B" denotes the size of the crimper.
B crimps the sizes shown by Whitcrane76, D is slightly larger with only 1 crimp hole as are the rest up to #6 size open wire.