Steyr changed to the rectangular bolt release with the MODELS 1924 and 1925, the "Hochrasanzstutzen" = high velocity rifles for cartridges like the .30-06, 7x64, 8x60, 9.3x62. Up to WW2 they continued to make their proprietary models 1903/6.5x54, 1905/9x56, 1908/8x56, 1910/9.5x57 with the original round-knob style bolt release. So the style of bolt release is not useable for dating a 1903!