A system of single weights and measures was introduced and in 1850 the Swiss franc became the Swiss single currency, complemented by the WIR franc in 1934. Article 11 of the constitution forbade sending troops to serve abroad, marking the end of foreign service. It came with the expectation of serving the Holy See, and the Swiss were still obliged to serve Francis II of the Two Sicilies with Swiss Guards present at the Siege of Gaeta in 1860.