If I'm correct, this is another version of the 1926-1937 silver mark:
The letter 'P' at the base indicates the assay office. It is known that 'A' is for Bucharest and 'L' for Muntenia, but other noted letters, 'C', 'N', 'O' and the 'P' remain unidentified at the moment.
The two strokes to the right of the 'P' indicate the purity, in this case 800/1000. A single stroke indicates 950/1000, and three strokes, 750/1000.
I'd be delighted to receive any corrections/confirmations