I'd imagine that its silver plated..
Trevor,
The Asprey model is definitely NOT silver plated!
After it was 'found' it was placed for safe keeping in a bank vault for a few years, then transferred to QE2 in the 1999 refit, so as to be able to be taken onto the ship's P&I. The reason for this was partially 'financial' and partially historical. Financial, to save bank and insurance costs, historical so that it could be placed on display on QE2.
It is also 'Hall Marked', so definitely not silver plated.
It is, if i remember rightly from what Commodore Warwick told me some years ago hollow, although made from fairly thick silver.