As far as I have found, the word "Tower" on Enfields has little or no meaning. It was a holdover from when arms were actually made at the Tower armory. Some manfacturers used there own name there (the better manufacturers, mostly), others used the word "Tower", and yet others used no words.

As for the Crown over VR, I have recently learned that this indicated that it was made to the registered pattern and standards (but does not indicate it was made under or for UK Government contracts).