As a result of my previous post arguing that there is a respectable case for a relatively early second independence referendum, a number of people left comments suggesting that we can't even think about doing that until we get the currency issue sorted. The reality is, though, that the complexity of the issue is reduced by the fact that there are only so many options open to us, and some of them can be swiftly eliminated for political reasons.
Option 1 : Apply to join the Euro. Might have been a vote-winner fifteen years ago, but now a complete non-starter.
Option 2 : Propose a common Sterling-zone with the rest of the UK, and decline to specify a Plan B if London refuses to agree to the plan. There is broad consensus that this policy was one of the weakest points of the Yes campaign last year (from a tactical rather than economic point of view), so a repeat can probably be ruled out.
Option 3 : Propose a common Sterling-zone, but have a clear Plan B to cover the theoretical possibility of a London veto. This falls foul of the very reason we were so reluctant to specify a Plan B last year - arguing the case for two completely different policies might not come across as terribly credible, and can be easily misinterpreted as meaning that we don't really believe Plan A will happen.
Option 4 : Use the pound outside a formal Sterling-zone. A perfectly respectable possibility in theory, but in practice leaves us open to more sneering about "Panama".
Option 5 : A Scottish currency pegged to the pound.
Option 6 : A Scottish currency not pegged to the pound.
As far as I can see, it's overwhelmingly likely to be either option 5 or 6, so it's just a question of war-gaming the two possibilities to see what would be most likely to stand up to intense scrutiny during the campaign. It might seem regrettable that the decision can't be made on economic grounds alone, but the reality is that the choice of currency has to command public consent, both before and after a referendum.