The Great Eastern was a ship with a fascinating history, too long to tell here. If you are interested, check out the listing in Wikipedia, which tells all, and is incredibly interesting.

She was launched in 1858, and at that time was the largest ship ever built, with a capacity of 4,000 passengers. The plaque was probably made just around the time of the launching.

The plaque measures 9" wide by 8" tall, and is in excellent condition.