National

I’m not sure of National’s history in regard to nixie tubes. They seem to make identical models to Burroughs, though they also seem to function better. However, they also made tubes unique to them, such as my favorite large nixie tube, the NL7037.

NL5441A

A smooth-topped version of the B5441/NL5441. This became very popular when a few Divergence Meters were built using this tube.

NL7037

The NL7037 is the largest American nixie tube. It is the same size as the Z568M.