DC-15s

Usually carried as a sidearm, the DC-15s is smaller and less powerful than the DC-15 blaster rifle. There a two main versions of the DC-15s. One- the DC-15s-is the sidearm variant.

http://www.geocities.com/ksw_img2/img_dc15ssidearm_img01.jpg

The other-the DC-15S- is a carbine rifle.

http://swg.allakhazam.com/images/schematics/dc15_carbine.jpg

The lower case "s" means sidearm. The capital "S" most likely means "small rifle".