The only Achille Lauro 2.50 chip I've seen is Chuck Mades' and it's an ad chip on the other side. If yours is a real chip, you have a treasure.

You may remember the ship as the one hijacked by terrorists in 1985, resulting in the murder of one hostage. The link below has the Wikipedia story on the ship. The ship caught fire and sank in 1994, so we most likely won't be seeing any of her chips brought back by vacationers.