Well, if this is what NGC considers an MS-63, I'd say your estimate is quite sound, in my opinion. NGC AU-58 https://www.ebay.com/itm/1907-B-Bri...327928?hash=item5d9c4e2e78:g:aBEAAOSwltNeX7ww NGC MS-63 https://www.ebay.com/itm/British-In...537877?hash=item2aab7a2f55:g:D8wAAOSwjzJbGwnY NGC MS-64 https://www.ebay.com/itm/INDIA-Edwa...459310?hash=item445c7cce6e:g:X0sAAOSwby5e4WrP