I'd examine the wiring inside the pin cabinet;

• What colour is connected to the earth braid (the sort of woven bare wire that runs to all exposed metal, side rails, leg bolt plates, coin door etc). most likely the green and so this will be the earth.  I'd verify this with a multimeter, testing for continuity
• find the line fuse - the first fuse that either your black or white wire goes to, this will be before the transformer and is likely to be near the line filter (a little silver box), this will be the active
• the other wire will be the neutral

If you post a picture someone will be able to comment.

The diagram below shows the plug connections and current plugs that meet standards are marked in this way.  A way to remember how to wire up a plug is the acronym "CLEAN"  When viewed from the back (the wiring side) of the plug the connections are, going CLockwise, Earth, Active Neutral.  The earth is the pin that stands up vertically. The corresponding wire colours are green/yellow for earth, brown for active and blue for neutral.