As the purpose of the PAT test is to make sure a plug is safe to use, then if the plug does not have insulated pins, then it is not safe to use, so should be replaced with a plug that meets UK Plug wiring standards.
This change in manufacture came about from an amendment on BS1363 in 1984, where it became a requirement that the line and neutral pins should have an insulation sleeve.
37 plus years later, equipment fitted with non-sleeved plugs is still found in use.
Plus, there is actually no guidance to say that a PAT tester has to replace these plugs – even the latest Code of Practice doesn’t make it clear whether changing is the right way to go.
Although PATTA’s Working Standards don’t directly refer to this topic we do expect our members to be putting their clients safety first, so plugs that are not safe should be replaced.