Cultural relics restoration is a subject one could study for a lifetime, and Leonard and his team had only gleaned the basics back in their day. Even though Leonard has since self-studied a considerable amount of this knowledge and mastered related technologies, his skills are still only at a fundamental level.
Fortunately, the task Leonard has to perform now is simpler than he initially thought. All he needs to do is clean up the rusted area where the cannon's rear might have inscriptions and carry out basic restoration work.
It's noteworthy that the cards are not all-powerful. For instance, restoration cards of any level can only repair things in their entirety; they can't selectively restore parts of an object.
Thankfully, Leonard's earlier study and physical strengthening mean he won't mess up while restoring such simple items. Therefore, the overall process is only slightly slower than using the cards.
