This plaque is for celebrating grand opening for a shop, usually for restaurants.
In the old days it was handmade and calligraphed (of course, when there were no personal computers). And required bamboo builders to scaffold the whole structure.
At the top there is the name of the restaurant, in the middle those big four words means “Grand Opening”. Those silver small words at the bottom are usually the names of investors or friends who paid for this plaque as a big gift.