Watch for the No Parking signs on Creekshore Trail
X 225 is the designation for a survey disc placed here in 1964. It is a US Coast and Geodetic Survey Bench Mark. Benchmark hunting is pretty close to geocaching except these things are designed to last decades. Why not fiind the geocache, then log the survey marker at this link which is also on the geocaching website; http://www.geocaching.com/mark/details.aspx?PID=AQ1401
I found the disc a couple of years ago, but it was totally covered in soil and grass. I had to probe with a tent stake and I finally uncovered it. I don't know why finding these old things is fun, but it is. Some of them are loggable on the site, some are not. Look at this link for more markers; http://benchmarks.scaredycatfilms.com/index.html
Some eventually get paved over or covered with rocks or bull dozed. Each has a datasheet that will give the history of the mark. Some are discs, others are metal rods injected into the earth. Others are chimneys, statues, or other landmarks. Good luck.