A note on the guinea. IIRC, it was originally intended to be a gold one pound coin. However, the value of gold went up just when it was issued so it was revalued higher by adding the extra shilling. I imagine the extra prestige associated with it was mostly about it being gold.
I've variously heard it was a 5% commission for the groom, jockey, or auctioneer. If a horse won a 100 guinea prize, the owner conventionally got 100 pounds and someone else got 100 shillings in commission.
I don't know about this aspect, but horse sales typically involved this type of commission. The buyer would pay in guineas (or £1.05 times the nominal purchase price) and the seller would receive that number of pounds, with the extra going to the auctioneer.
I'm not sure if this system persists now, but it definitely lasted long past decimalization.
