A320 is commonly used and best described as a spec for Anchor Bolts being used in cold temperatures that have high impact results in low temperatures. A common application for A320 is for pressure valves, flanges, valves and fittings all for low temperatures. 

Recommended Nuts and Washers: 
A194-L7 or L4 Nuts for the L series of the spec
A194-8, 8C, 8T, 8F, 8M, 8LN, and 8MLN
Washers are to conform to F436