Be very careful with your threat model here. If an agent attempts to use the codes and they don't work, and they find out there's a dual pin mechanism, you could end up in more trouble than with whatever they'd have seen in the first place.
And, if you do, and you're really asking hacker news for opsec advice, I would suggest you abandon your career as a super-spy or whatever you're doing, because you're doing it very wrong.