[Amps] Help with balun core please

[Steve Thompson]

I wonder if anyone can identify a manufacturer or likely part number for me?

I have a two hole balun core, .5" x .5" x .25" It has green paint on one 
of the flat faces. I'm fairly certain it's of US origin. I've seen other 
cores the same size with red paint on them.

Does any one know who colour codes their cores this way? I know 
Micrometals uses colour coding, but they don't appear to make balun 
cores of this size.

Thanks,

Steve