Parallel straight raised lines are indicative of die polishing. Single non-linear lines are more likely to be cracks in the die surface as it starts to break up.
The second I in BRITANNIAR vertical centre line is pointing to a gap between two teeth rather than at a tooth. Suggest you buy a copy of Davies where all will be explained, plus all the other pointings for all denominations of silver (including Cu-Ni) from 1816 to 1980.
Thank you for continuing the story............
Other than this thread, what brings you back?
Great to see you again. Pull up a chair and share what else you have detected. Always interested to learn.......