Although trains and accessories of similar gauge or scale existed as early as 1927, modern commercially produced N-scale models were first launched by the Arnold company of Nuremberg in 1962. Unlike other scales and gauges, which were "de facto" standards at best, within two years N-scale manufacturers defined the gauge and voltage, as well as the height and type of couplers. For example, Arnold developed the now ubiquitous "Rapido" coupler to provide a simple and robust releasable coupler design. Although the original Arnold coupler has been joined by more functional and aesthetically pleasing designs, Arnold allowed use of the Rapido design by other manufacturers, so established a common standard to couple together rolling stock from different sources.