E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
Penny (in the sense of pound).
Sixpenny, eightpenny, and tenpenny nails are nails of three sizes. A thousand of the first will weigh six pounds; of the second, eight pounds; of the third, ten pounds.
1
Penny sometimes expresses the duodecimal part, as tenpenny and elevenpenny silvermeaning silver 1012ths and 1112ths fine.
2
One was to he tenpenny, another eleven, another sterling silver.Weidenfeld: Secrets of the Adepts.