Its going to sound very cumbersome, because it was. Making celluloid was a dangerous and dirty artisan craft - it was master craftsmen who did some of the most remarkable celluloids.

For vacumatics they stacked alternating sheets and cross cut that stack giving a striped pattern.

But these look like what they might have done is run some sort of tool (like a brush) across a soft celluloid sheet, perhaps when they were adding pigmentation. Its a guess, really - I would have first thought it was made like a vacumatic, but the stripes are crude and not straight as if they were done by hand. Once the whole sheet was done and dried, they would have cut it up into small pieces and randomly arranged it, softened it with solvent and pressed it into a new sheet. They would have then waited for it to dry, cutting it into strips and fabricating the barrel using a helical weld.

I'd be willing to bet that the craftsmen who did these sheets all had their own techniques that they refined over time. I think about Parker's Golden Web celluloid, and just twist my brain into knots trying to figure out how they did that.