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

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.