Mills 12 watt audio resistors
Some values maybe marked MRB-12-NI-CU
which were later changed to MRA.
Construction is the same and maybe considered vintage Mills.
There are 3 variations made by Mills:
Dull black coating
Shiny black coating
Semi-gloss red/brown coating
The Central Resistor made version
had a semi-gloss red/brown coating,
marked only with "MRA".
These maybe the best version of the Mills
audio series wirewound.