Currency. Weights. Distances. You’re going to be doing a lot of math on the road. Speed limits may be posted in km/h. How many dollars did that 14 dinar dinner cost? You bought how many kilos of peanuts? Probably too many.
Take note of conversion rates. Bring a calculator with you. Perhaps pack one of those Mead folders with conversion charts. Whatever it takes to justify carrying around your Trapper Keeper.