A nice looking Luger that has an Erfurt toggle train and frame but the trigger has been replaced (different number) and the barrel is a replacement.
The lack of a date likely means it was reworked post WW1. Caliber is impossible to determine from your pictures but the fact that it's been re-barreled suggests that it MAY be 30 caliber (7.65mm). Many WW1 9mm Lugers were converted to 30 caliber and use a cartridge like the bottle neck ones below. On the far right is a 9mm.
