"My conversion table [Pocket Ref by Thomas J. Glover, no desk is complete without a copy!] lists your conversion number under "gallons (US dry)" "

That's very interesting - the number I quoted was the conversion for imperial gallons (the gallons we use in the UK). It just surprised me that the US gallon was smaller than the imperial gallon when usually things in the US are bigger than everywhere else...

We are sometimes forced to work in bastardised units such as decimal feet (1' 6" == 1.5 feet) as customers in the US refuse to use metres but can't cope with the inconvenient fact that there are 12 inches in a foot.