@redweasel  
Yeah, in fact looking at this I’d say it was back when I still sketched & inked on paper, with only a single fine-marker, then scanned it in.  
Later that I bought a bunch of different thickness pens, and started playing around with line width.  
These days I tend to work digitally all the way through, so I’ve kinda drifted back to a single pen-brush, but with pressure-sense on the width. Even more lately I’ve been playing around with actually using different brushes and brush widths for the lines.  
It’s been a journey.

I notice all the lines are the same thickness. really changes things when you start paying attention to that, huh?