Here's an example of why I think it might not be vector. Corner variance.

A skilled draftsman will generally not have any trouble to draw things cleanly like that, with or without vectors doesn't really matter.

It is still entirely possible that it was done with vectors though, e.g. using the freehand tool, or that it was drawn as bitmap and then auto-traced to get the linework to look crisp at high resolutions. The corner variations could be produced just as much by a bitmap brush as by a vector-tool. It could even be drawn on physical paper with a stabilo/fineliner and then scanned, who knows.

Perhaps what you really wanted to know is whether this was drawn with the bezier tool or the freehand tool? In that case, the answer is most definitely that it was drawn freehand, possibly with a little bit of stabilization enabled (but not much -- you can see many micro-wiggles in the lines).

>>250842
Illustrator using the 'Artistic Brushes' Palette