Have been sorting my posters the last few weeks and had a chance to compare 2 Porco Rosso posters I have.
One I got a few years ago and has been sitting in a poster file.
The other I got about 6 months ago.
At the time, I didn't know about the Ghibli Museum selling reprints of the movie posters.
Pretty sure, that the new poster I got is a museum reprint.
On the reprint, the colors are not as deep, the clouds are not as defined and the paper feels thicker and with less of a sheen than the original poster.
When laid side by side, the difference in the sky and cloud colors are quite apparent. As well, the main title is a much lighter / orangish red.
In the pictures, the reprint is on the left and the original is on the right.
Luckily, I didn't spend much on the reprint!