Forbidden Zone Geocaches
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  Silverback Cipher  
Silverback hunters should be familiar with the “pigpen” or masonic cipher, which is a simple substitution cipher exchanging letters for symbols based on a grid.

This cipher can be used to decrypt directions and secret codewords at FBZ geocaches!

  External Links  
  · 1: The FBI Vault
· 2: The CIA Vault
· 3: Project Blue Book
· 4: Aliens the Truth

The Bunkers
FBZ A.P.E. 52(a) - GC9WHDE

Read the mission brief below...


SUBJECT: FBZ A.P.E. 52(a) Brief [Mission #2(a)]

TO: Silverback Operatives

The fortifications at this location are said to have been erected shortly after the Japanese attack on Pearl Harbor in December of 1941. They are often referred to as the “Camp Minnewawa bunkers” because a Civilian Conservation Corps (CCC) work camp named Camp Minnewawa operated in this area around 1937. The CCC built the mountain trail you traveled on to get here.

Camp Minnewawa (Dec 1934) The CCC camp is said to have closed in 1942. Allegedly, the government seized the land from Birch through eminent domain around 1943 in response to the Pearl Harbor attack. The military is said to have built these bunkers to house radar units and generators that powered them. The military also built the concrete structure below to serve as an artillery bunker. This site was only commissioned for a short time and returned to the Birch family in 1947.

S.G.T.F. was unable to find any histoical records acknowledging military use of this land. It was not documented in a historical site assessment made for the Otay Ranch Company in 2009, nor was it mentioned as a harbor defense position in a military historical record compiled by Steve Schoenherr of the South Bay Historical Society.

Why? Well, we believe these bunkers served a completely different purpose. Why do these bunkers contain bars on their doors and why do they look like prison cells? Why isn’t there evidence of old military communications equipment scattered on the surrounding hillsides? Is it really feasible artillery mounted here would reach the San Diego coastline in lieu of an attack?

No, friend. These bunkers were used for a more sinister purpose such as alien-primate genetic testing. Or perhaps they were erected by advanced bi-pedal primates to jail human prisoners. They might even now serve as the entrance to a doorway leading to an alternative universe where reptilian extraterrestrials breed intelligent primates to battle human beings.* Possibilities are only limited by a retardment of imagination.

In all, there are seven (7) FBZ locations (i.e. missions) to Operation Silverback. Six FBZs contain “intelligence” report(s) and a corresponding secret codeword. Use the six (6) codewords collectively at to discover the seventh and final TOP SECRET FBZ location. Keep in mind codewords can be gathered in any order so you DO NOT need to visit FBZs sequentially! The seventh and final mission location is where the truth shall be revealed!


Operatives who have successfully submitted the TOP SECRET codeword for this mission...

  • Honorable Discharge THEJJDUO
  •  (Mon 26 Jun 2023 @ 21:53:37 BST; 1687812817 seconds since Unix Epoch (POSIX) 01 Jan 1970 00:00:00 UTC)
  • Honorable Discharge FLAGMAN
  •  (Thu 01 Jun 2023 @ 22:04:00 BST; 1685653440 seconds since Unix Epoch (POSIX) 01 Jan 1970 00:00:00 UTC)
  • Green Beret STANSD
  •  (Wed 28 Jun 2023 @ 13:22:18 BST; 1687954938 seconds since Unix Epoch (POSIX) 01 Jan 1970 00:00:00 UTC)
  • Green Beret DICKANDALE
  •  (Sun 17 Mar 2024 @ 20:57:12 GMT; 1710709032 seconds since Unix Epoch (POSIX) 01 Jan 1970 00:00:00 UTC)
  • General MPARK65
  •  (Tue 11 Jun 2024 @ 18:39:04 BST; 1718127544 seconds since Unix Epoch (POSIX) 01 Jan 1970 00:00:00 UTC)
  • General MAGICN3
  •  (Wed 12 Jun 2024 @ 11:17:32 BST; 1718187452 seconds since Unix Epoch (POSIX) 01 Jan 1970 00:00:00 UTC)
  • Major General MIKE2FIND
  •  (Sat 15 Jun 2024 @ 18:18:14 BST; 1718471894 seconds since Unix Epoch (POSIX) 01 Jan 1970 00:00:00 UTC)
  •  (Fri 21 Jun 2024 @ 14:48:52 BST; 1718977732 seconds since Unix Epoch (POSIX) 01 Jan 1970 00:00:00 UTC)

Mission 2 Report

FBZ A.P.E. 52 contains a large ammo can with Special Reconnaissance (SR) related to SGTF's Operation Silverback in the form of Planet of the Apes Memorabilia (POTAM) and scouted intelligence reports. As a clandestine special tactics unit, SGTF has been known to leave POTAM tracking bugs in FBZs with special mission instructions related to active Project A.P.E. caches (e.g. Project A.P.E. Mission 9: Tunnel of Light).

FBZs are reserved for POTAM related to SGTF's Silverback operations. Visitors are encouraged to register their visit and leave ONLY items containing relevance to The Planet of the Apes or items that are traditional hitchhikers (e.g. geocoins, travel bugs, etc.). Only place and/or remove TRACKABLE items from this cache (read NO unrelated SWAG); Any POTAM found in this cache designated as NOT TRACKABLE is pertinent to operations for this FBZ and should REMAIN ASSIGNED TO THE CACHE. POTAM labeled PROVISIONAL FTF is considered remittance as reward for the FTF (First to Find) and can be removed freely without restriction or stipulation.

Copyright © by Forbidden Zone Geocaches All Right Reserved.

Published on: 2023-05-29 (856 reads)

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   Operation Silverback Prize Ring SILVERBACK Prize Rings

Those who create an account on and enter mission codewords and POTAM tracking bug numbers receive points towards an Operative ranking. Operatives who achieve the rank of General (700 points) are eligible to receive an official silver Operation Silverback trackable ring from Oakcoins. Gold rings are available for those who reach the rank of Green Beret (or higher).