The grooved prewar style rear bridges were not factory drilled unless special ordered and you would need proof of that.
That being said yours looks like the smooth later style rear bridge and most were factory drilled. There are a very few smooth rear bridges with no holes or only one hole, but they are extremely rare and more likely to occur on H&H length actions.
From what I can see it is a beautiful example, original, unaltered,that has been used. I would be proud of that one myself!
