Could be sweat from the rollers...... Gross...
Fwiw, in the 1920's & 1930's the machine made cigar companies ran a HUGE advertising campaigning about the "health risks" of worker sweat and spit in handmade cigars and why everyone should smoke machine made cigars untainted by human hands. It actually made a real dent in handmade sales... but then the reality of how disgusting some of the machines were got out and the campaigned died.
Today, I think both the machine made and handmade manufacturers are extremely conscious of keeping their operations sanitary.
I can tell you one thing, we go through a whole lot of anti-bacterial soap in a handmade cigar factory - it is like running a restaurant, cleanliness is critical.
Keep in mind that guys like me smoke the exact same cigars we sell, so we pay very close attention to anything health and welfare related - it is one of the things I like most about the premium handmade cigar business, all the execs and owners are fanatical consumers of their products - we love cigars too!
BR,
Steve Saka
CEO, DE