As stamps aren't something that got used much in Derbyshire, I can't claim to know a great deal about them and was just going by the photos in Gerrard's book on the early tin industry as to what remains you might expect from a stamp mill - shame they didn't read it first either, or look more closely at the pics from Agricola!
The bit that really got my goat was the faff about the knockstones being evidence of early mining, the damn things were used on small mines well into the 19th century and for that matter, widely used in the 18th at some quite substantial mines going by the records for places like Odin and Portaway!
Follow the horses, Johnny my laddie, follow the horses canny lad-oh!