They'd have not forced license plates to be displayed at all times to begin with, as they are a search of your papers without probable cause your vehicle is unregistered. Private ships in those days (probably the closest equivalent of something big and dangerous that could do tons of damage quickly on the public right of way) did not have required hull numbers or anything like that. Of course that doesn't totally solve the flock problem, but makes it a lot harder.

Ships then, and now, don’t really need numbers for identification. There are various unique numbers that they can and do use occasionally for specific purposes(IMO numbers and hull numbers). However, a ship’s name and home port were, and are, more than sufficient to identify a ship for legal purposes. You don’t need a registration number on a ship, and certainly wouldn’t have needed one then.

The authorities absolutely kept meticulous records of ships entry and exit from any harbour as well as what was on board, what was loaded and unloaded and frequently a list of all persons onboard.

Some flag states enforce uniqueness constraints on name and home port combinations. The US does not, but that really doesn’t matter much in the real world. There just aren’t that many conflicts.

More importantly, the founding fathers very much did not extend privacy rights to ships. Intentionally so. The very first congress passed a law in 1790 that exempted ships from the requirements of needing a warrant to be searched.

The ability to track and search ships without warrants has been an important capability of the federal government from day one.

Hell, the federal register of ships is published and always has been. I don’t know how they would have felt about private cars, but the founding fathers revealed preference is that shipping and ships are not private like your other “papers and effects” are.

The comparison to private ships doesn't quite land, IMO.

Ships - ships big enough to do material damage would be very small in # - ships big enough to do material damage would have a (somewhat?) professional crew - whatever damage they could do would always be limited to tiny areas - only where water & land meet, only where substantial public or private investment had been made in docks/etc - operators have strong financial incentive to avoid damaging ship or 3rd party property (public or private)

Cars - in some countries the ratio of cars to people is approaching 1 - a vanishingly small portion of vehicles have professional drivers - car operators expect to be able to operate at velocities fatal to others on nearly 100% of land in cities, excepting only land that already has a building on it, and sometimes not even that. - car operators rarely held liable for damage to public property, injury, or death and there's strong political pressure to socialize damage and avoid realistic risk premiums

I don't love flock but IMO the only realistic way to get rid of license plates would be mandatory speed governors that keep vehicles from going more than like 15mph. I would be fine with that, but I suspect most would not. If we expect to operate cars at velocities fatal to people outside our vehicles, then there will always be pressure to have a way of identifying bad actors who put others at risk.

> Private ships

Often, the same people crying about Flock will decry private arms ownership through mental gymnastics.

These very same ships you speak of that could do "tons of damage" had actual cannonry - with no registration or restrictions on ownership or purchase, either.