Dear Charles

The Useful K. Almanac does not contain fluid measure as used by Apothecaries & the London Pharm:² says nothing (for us), except that the pint contains 20 oz. Taking the oz as $\frac{1}{20}$ of pint it = 437.5 grs the same as you have it & the pint 1$\frac{1}{4}$ lb. The rest is hypothetical if P’ = old pint = 1 lb (as we thought) then

^P’/16 = ^{P(imperial) /20}, or

16 oz (of 437.5 ^grs) = old pint

20 oz (of D^o) = imperial pint

I looked in my old Duncan & found the same discrepancy underlined.³

It is enough to make one swear | E D