Steel alloys include no more than 1.00 percent by weight of silicon, 18.0 to 22.0 percent by weight of chromium, 1.80 to 2.50 percent by weight of molybdenum, 0.01 to 0.10 percent by weight of nitrogen, no more than 0.01 percent by weight of titanium, no more than 0.01 percent by weight of niobium, no more than 0.01 percent by weight of aluminum, the remainder being essentially iron. The alloys are ferritic but polishable and have mechanical properties that nearly match those of the standard steel alloy no. 1.4521. The steel alloys are processed into watch parts such as housing bottoms, housing shells, and faces, among others, such that watch housings produced from the alloys magnetically shield the clockwork.