That looks like the standard striker plate! Looks like it has been moved down-did the door sag? If you take the outside lock off, there should be a number stamped on it. You can order a new key from
Scamp, or order the entire outside mechanism from
Scamp. As Donna pointed out, a garage door handle with lock(available at Lowes or Home Depot) will work also.
I ordered a new lock from Scamp and turned out the key for the new lock fit the old one too(not a good thing).