It looks to me like an Ikoflex Ia (model code: 854/16). If that's correct, then it was most probably made between about 1952 and 1956. Maybe the factory was still using up old camera bodies that had been manufactured before World War 2, but that were then shelved, if the factory was converted to making military equipment in the war years. If the serial number is definitely pre-war, that might possibly explain it. As for the lens... maybe the original one got damaged and a previous owner replaced it with a lens from an older model (which is a possibility, because I believe the lenses can be removed by unscrewing them).