That article isn't good at all IME ItsAllGoingToBeFine.
It also assumes that the currency is an asset. The actual currency reserves i.e. the physical money in the bank, could be argued to be an asset certainly - but the currency itself...see below.
Uk govt analysis (sorry it's long, there wasn't a sensible bit to cut without losing content!):
"It is right to say that the international law principle of equitable division applies to certain UK assets and liabilities and that this principle would be important in any negotiation should Scotland vote for independence. However it is wrong to say that an independent Scotland would be entitled to share the continuing UK’s currency, the UK pound, as part of a formal currency union. There is no rule or principle in international law that would
require the continuing UK to share its currency with an independent Scottish state. The system of currency used by a country is not part of its assets, as is explained below.
In the event of Scottish independence, the UK (without Scotland) would be the continuing state in international law. A detailed legal opinion from world-leading experts Professor James Crawford and Professor Alan Boyle was published with Scotland analysis: Devolution and the implications of Scottish independence, which set out at length a number of consequences that would arise from this position.
A.5 As a continuing state the UK’s laws and institutional framework would continue uninterrupted by Scottish independence. National institutions currently serving the people of the UK, such as the Bank of England and central government departments, would continue to carry out functions in the continuing UK and deliver services to the people of the continuing UK as before. Such institutions would have no jurisdiction in Scotland and
no power or obligation to act on behalf of an independent Scottish state. This means the Bank of England, as a UK institution, would remain the central bank for the continuing UK but not a new Scottish state. So it would only issue currency and set interest rates for the continuing UK and not for Scotland.
A.6 The position is quite different in relation to the UK’s assets and liabilities. The relevant assets and liabilities would, according to international law principles, fall to be equitably divided between the continuing UK and an independent Scottish state. The apportionment
of the UK’s assets and liabilities would likely constitute a large part of the separation negotiations that would necessarily follow a vote for independence.
What this means for the UK pound as a currency
A.7 It is important to be clear what the UK pound as a currency is and why it is not an asset. A currency is a system of exchange, a unit of purchasing power that works when others recognise it as having value. Currency does not have to be the coins or bills which are used by most states; it could be anything that people agree represents value. The UK
pound is underpinned by a legal, institutional and administrative framework which enables it to function as a medium of exchange, a store of value, a unit of account and a medium for deferred payment.
A.8 In the UK, as in most cases where a sovereign state has its own currency, the central bank has a monopoly right to issue money for its own area of circulation, including regulating the issuance of Scottish and Northern Irish bank notes by retail banks. The production of currency is regulated through legislation passed by the UK Parliament and monetary policy set by the Bank of England. Therefore, the currency of a state is inherently linked to the institution of the central bank and the particular monetary policy in that state – and the UK, the UK pound and the Bank of England are no different in this respect.
A.9 The sorts of assets that may be subject to negotiation in the event of a vote for Scottish independence are the cash, currency or gold reserves held by the UK state. These assets are very different from the system of currency itself; the particular currency used by a state is not an asset on the state’s balance sheet which can be divided up like the money in
a bank account. An individual pound is an asset, as is a collection of pounds in a bank account. The pound as a system of currency is not.
A.10 The Scottish Government has itself identified the UK Government’s Whole of Government Accounts as the basis of assets for which an independent Scottish State would seek to negotiate. Whole of Government Accounts does not include the UK pound."