A warship’s magnetic condition is not a property conferred at delivery. A steel hull, its diesels, its generators and every ferromagnetic component installed in it distort the earth’s field in a way that a mine fuse can read, and that distortion changes as the ship is built, altered, repaired and used. The condition can be measured, and it can be treated, but neither operation settles the matter permanently: a navy that wants to know whether a given hull still meets its magnetic requirement must be able to measure it again, against a configuration it can identify, using instruments whose own accuracy is controlled, and must then have someone with the authority to accept the result. That sequence is an industrial and administrative system, not a single asset, and it is the reason the familiar question — does this country have a magnetic range? — is the wrong one. The right question is where in Germany, the Netherlands and Sweden the segments of that evidence-producing chain actually sit, who owns and renews them, what the open record permits one to say about their availability, and whether a result produced in one country can be used by another. The answer matters beyond the mine-warfare community, because European fleets are simultaneously ordering new hulls, extending the lives of old ones and modifying both, and each of those acts creates a configuration whose magnetic evidence has to be produced or renewed by an infrastructure that almost never appears in a shipbuilding contract.