Its all explained here - according to the code EN636-2 it is class 2.
Specification of Plywood and Performance Criteria - Hanson Plywood
Specification Plywood used in the UK is sourced from all over the world and is often manufactured to overseas standards. Plywood manufactured for construction purposes is specified in accordance with EN 636. Products claiming compliance with this standard must also carry the specified markings...
hanson-plywood.co.uk