I agree with Bob on this one, I believe that the test holes were done with a firearm, most likely with a 303 as Bob suggested. My proof to this theory is the fact that all test holes done on 1824 in particular still have trace elements of lead in the test holes and they are not all unison in size or shape. If they were done with a punch or a rivet gun etc. all the holes would be perfect and unison in shape. I know for a fact that the holes were put in 1824 before construction and are not battle or post-war related because they are mostly in spots that would be impossible to shoot or 'test' once the carrier was assembled. The steel in a LP2a would have been designed to stop rounds up to .303 in calibre so if you were going to test the steel during construction, if would have been quite simple to just discharge a .303 at it and find out wouldn't it?
Nathan