According to a 2016 post by Ted Walther:
http://www.ptboatforum.com/cgi-bin/MB2/netboardr.cgi?fid=102&cid=101&tid=3591&sc=20&pg=1&x=0

PT 506 was one of several boats "stricken and destroyed" in 1954.

His source is "Allied Coastal Forces of World War Two: Volume II Vosper MTB's and U.S. Elco's" By John Lambert and Al Ross II.



Jim