This series of caches are located along the track parallel to the agricultural railway at the South Kulin railway siding. The attached map from 1935 shows the siding is 230 miles from Perth linking in with existing early 1900's networks.
At the posted coordinates, cache is a very short distance away!
It can be found at:
S 32° 43.(476 minus the number on the sign)
E 118° 5.(410 plus the number on the sign)
Take care around the rail line.