[PowerPro]

Very interesting. Thank you!

[mamelukesabre]

check wikipedia for “pennyweight”. It equals 1/20th of a troy ounce. A troy ounce is 1/12 of a pound.(not your standard 1/16th of a pound for a regular ounce)

Then if you really get interested, you can look up avoirdupois weights and measures and contrast that to apothecaries weights and measures.