The cache may not be at a trig beacon but it is situated on top of a hill where a trig beacon would normally be found and next to something that has to do with numbers (like a trig beacon but in this case in a different context).
To retrieve this cache a flat tool is required so please don't try and force it open without one. Make sure it gets returned exactly as you found it to keep its camouflage in place.
The "Not the series" series is made up of:
Not the Seaview Series
Not the Trig Beacon Series
Not the Disney Series - archived
Not the Postbox Series - 3.0
Not the Heroin Series - Cousin Penny - archived
Not the Urban Park Series
Not the Snail Trail Series
Not the Walmer Challenge Trail Series
Not the Afrikaans 101 Series
Not the Optical Series
Not the Borders Series