What's the boldest variant of the "Neuzeit?"
Neuzeit Grotesk (or "GroT") is the boldest I've found online, but I just came across a sample in an illustration that was even bolder than that. I need to be able to match it.
Normally, "Black" is used to mark the heaviest (boldest) variant of a font. Or, they use a number scheme, usually running from 100 (lightest) to 900 (heaviest).
So, I'd expect Neuzeit Grotesk Black to be the heaviest variant:
The 'grotesk' part of the name simply refers to the stylistic family of sans serif it is from. http://en.wikipedia.org/wiki/Grotesque_(typeface_classification)
If you can't find a match, it's possible that whoever made the illustration you're talking about manually tweaked the font or added a stroke to it to make it heavier.
There might be giveaway hallmarks of a stroke being added - for example, the sharp point of the M would be either rounded, flattened or extended if a stroke was added depending on the stroke corner settings/mitre limit.
Can't say any more than that without being able to see the illustration or see what the heaviest variant you've found is.