All Evo bikes were made pre '85...
Actually, that's not quite right -there's plenty of post-84 Evo legal bikes. DT175s, 513 CZs, CT110s (
), TS185ERs, XL185s, etc.
For Evo and Pre-85, the actual year of manufacture
does matter because neither class has 'follow on' model provisions.
The more I think about it, the more I think that Evo should actually be pre-81. As much as I think that Evo is a brilliant concept (structuring the regs around technology criteria rather than age), while it is the only class that's defined like that, it creates a truck load of dramas (as this thread demonstrates).