i have a few brass plates with boat details they are from my dads ex navy boat is there an easy way to get them looking like new i was thinking of steeping them in cola is this a good way
Cola works. I once had to recondition an old brass curtain track and fittings, and charged for a bottle of Coca Cola, they came up beautifully. However for brass plate I would do that first, maybe, but then use what the army used to do with hat badges etc. Scrub it with a nail brush and washing up liquid, then use Brasso.
If you are thinking about monetary value or long term preservation the polish is not good museum practice. Polishing metals wears them away. My mum's warming pan had a peacock design on it 60 years ago. Now it hasn't.