You are referring to an exchange rate Bustino, this is just changing one unit of measurement for another, what you are purchasing however is not an asset just another unit of currency WHICH then you can buy assets with in your new unit, so to explain using your example a dollar and a pound are both units of measurement and if you exchange a dollar for a pound you get a variable amount of the other depending on the current rates.
Currency as measured by the above units can be used to buy assets such as property or goods or services but you can not divide the unit of measurement in the way AS was asking. What he wanted was permission to use the same unit of currency and when refused stated we had no right to refuse as it is an asset. It makes no sense. You can share a certain sum of currency such as £10 but it's value is only due to what it represents as purchasing power not the unit itself. So what we could divide with Scotland is everything that has value but you cannot divide the unit used to measure the value.
Were you to be married and then divorce there will be a division of assets, you will likely divide property, savings, investments etc , you would have negotiations upon how much each asset was worth using the local unit of currency and then a division of each, you would never raise the question with your ex-wife of sharing the unit itself in which the value of the property were measured because it is nonsensical. You could divide the sum of savings but again they only represent their purchasing power.
We all knew what AS meant but his request should have been honest and put like this
We need to use your currency which is backed by the Bank of England as if we don't we have no alternative which I could promote with any real credibility at present, I need something to persuade you to allow me this and I have some bargaining chips which I am now going to attempt to use. I will walk away from my percentage of the debt we both ran up if you don't let me. I don't actually want to be so humble as to recognise I am asking you for something however you see, so I am going to dress it up as our right, to do this I am going to claim it as an asset.
So my claim is that sterling is a unit of measurement and cannot be divided in itself and that what was sought was permission to use it. If you are claiming sterling itself is an asset how much is it worth? and what unit are you now using to measure the previous unit?