There are no signs of any London marks on the barrels that I can see in the photo .Usually the London provisional mark was in the rear centre of the flat and quite deep , so even if the old marks had been filed off which would seem strange ,I would expect to see some sign of the originals . From this I drew the conclusion that the barrels we see are not original. Either the gun has been re-barreled or had an additional set made and these are the ones you have now .