To find the cache, locate the bench at the coordinates given.
The dedication plaque has two dates on it...
ABth August CDEF - Gst September HIJK
The cache can be found only a short walk away at
N((D+E)xK)-1o (Bx(B-A).((H+E)!-K2)
W 000o 0 (K+G).(((DxF)+C)2+A)