This is not the greatest trig in the world....this is just a trigute.
I love trig points. Absolutely love em! I was utterly delighted to find this beauty round the corner from our house.
Now, technically this isn't a trig, it's a fundamental benchmark (click the name for more info) but let's not split hairs, it's still awesome! I've never seen one like this, so come, geek out with me 
To find the cache you'll need to gather info off the minitrig...
The cache can be found at...
N 53 37.ABC
W 000 13.DEF
A = number of letters on the OS base plate. 3rd line down, first word.
B= number of letters on the OS base plate. 1st line, 2nd word +1
C= What's the sixth number of the phone number?
D= number of letters on the OS base plate. 1st line, 7th word
E = number of words on the bolt (top of the pillar)
F= number of words on the embedded metal plate on the right side as you look at it?