The price of a case (five shillings piece bad) from the smasher is about one shilling; an alderman (two and sixpence) about sixpence; a peg (shilling) about threepence; a downer or sprat (sixpence) about twopence.1859, Snowden's magistrates assistant, page 90:
Etymology From Middle English sprotte, from Old English sprot. Older source is unknown. Cognate with German Sprotte, Dutch sprot. Compare sprout.
1
Historical To manure (land) with sprats (the fish).
[…] spratting the land. This treatment is supplemented by about half a ton of artificial manure, largely made up of a mixture of superphosphate and some nitrogenous manure.1923, The Agricultural Gazette and Modern Farming, volume 98, page 190: