I can't remember the source (drat!), but I do recall reading that in JA's time people would often refer to the cost of luxury items--like a horse or a carriage--in guineas, rather than pounds. Seems appropriate somehow. But all else would usually be designated in pounds.

This may be unrelated--my grasp of finance is tenuous at best--but your question reminded me of the gold shortage and wartime inflation which grew critical in 1812, I think. (Wellington was having a good deal of trouble getting the financial support he needed that year.) There was an outcry in Parliament about returning to a gold standard since it was thought that too much paper money in circulation was unwise. But in any event, I don't think Parliament ever did return to the gold standard.

I was wondering if any of the above would have had anything to do with the phase out of the guinea?

This is probably in a muddle. Sorry! Nor can I recall the specific sources at all today.

Suzanne