What's the basis of assigning LTO plates? (preferably answered by Philippine motorists)?

Question

In the Philippines, vehicles registered on the 80's were given plates starting on the letters N and P. On the 90's, the letters started at T - W. What is the basis for this? Why is the letters Q & R not used (since S are for gov't use only)?

Answer 1

If you want a philippines answer, you should have posted it on the philippines board.  YOu posted on the USA board, and we have no clue.