Target E

One US Submarine was designated "Target E" as its official name.  It was never actually used as a target.  This was the last time the "Target" designation was used.  There were "Targets A" through "Target E" .  The submarine was the only submarine so designated. 

What was the submarine's name?
Why was the use of the 'Target' designator discontinued?

Target E was the ex-USS A-1

Twas in 1921-22 time frame.  Up to that point there were generally few ships that were to be used as targets and few that were available for disposal.  However, the post WWI disarmament and treaties that restricted the numbers of new ships that could be built meant that there were many more hulls available for disposal.  The Navy decided to discontinue the use of Target X designations because they would run out of letters.  The decision was then made to simply use the "ex-USS Ustafish" type designation and not further denote status as to whether a particular ship was to be used as a target.  It is of interest that within two years we used nine submarines as targets. All went down with their original name.