I know that the P refers to design by Sven Palmquist - pre 1980, after which they would have used SP.
The absence of a following letter may mean it is not glass & is therefore crystal - but I am not certain.
The 2405 would be the design number and the remaining numbers I assume refer to a particular variation of the design. For instance if it had an engraved design on it each different engraving would presumably have a different number.
Ross