Vengeance Range. A rummage in the bookshelf also gave some variable answers.
Putnam's Aircraft of the RAF since 1918 (Thetford)
1,200 as already stated.
Putnam's US Military ac since 1908 (Swanborough & Bowers) gives, for the A-35B,
2,300 st. miles
Salamander's Encyclopaedia of Combat ac (Gunston) says "Typical
600 miles".
Opinion is clearly divided on the subject, but think I'll stick with
Danny42C as the most reliable source!