I didn't know what to call this cache until I viewed the location on a map. It is almost exactly on the Ventura/Los Angeles county line.
You are looking for an ammo can with a few trade items. Please re-hide it well, I do not wish to carry another one up here. 
There are many trailheads you can take to get here, I used the one listed below, Las Virgenes and Morrison Rd.
Stay on the trails all the way to the cache. Cache is at 1223ft. elevation.
I walked up to the water tank and it looked like you can continue over to the trailhead that is at the end of Las Virgenes, but don't take my word for it.