It think it's probably more like late 1920s than pre-WW1. As to value, these always seem to sell for less than I think they should be worth, since they are enormous fun to shoot, accurate and quite powerful in good fettle. They rarely seem to sell for more than £130 or so, even in good original order. Like the similar sized Haenel mod II, a lot of them were exported to the UK and no doubt this depresses the value.