>European ship cannons were perceived to outrange Japanese and Indian cannons because the Europeans were always a step ahead on daring to reduce windage, because of trust in their production processes.

Their guns probably did have better windage thanks to superior manufacturing (to achieve such boring precision, they literally used a lathe big enough to turn a cast cannon against a boring bar), and better gunpowder too, but being able to create a 1:50 windage to bore ratio cannon tube doesn't automatically spell out to the ability to mass produce interchangeable parts, especially when said parts called for reproducing machined dimensions to a hundredth or thousandth of an inch accuracy, which again something that wasn't worked out until the mid-1800s.

Interesting you bring up Roman coins, because I recently read that the debased "silver" coinage of the late empire (when silver supplies had depleted) were basically just copper coins washed in silver salt to give them a silver coating that was so thin that it rubbed off after moderate use. As the coins had to be stamped after the silver washed, for good reason any stamped impression made on them couldn't be too sharp or deep, lest the silver wash would be damaged and the copper base be exposed, exposing the farce.