T/W stands for T. Williams (company name). Superslim is the Brand. AF stands for "Across Flats" of the fastener... (Different from BSW - British Standard Whitworth, which indicated the diameter of the bolt, not the width of the nut...).
Installed the Shimano Ultegra 10 speed Cassette I already had, Bought new Quick Release Skewers. Went for a ride and the skewers started loosening while riding. Had to stop and strongly cinch them down (with more force than with "normal" skewers). Replaced the rear skewer with a DT-Swiss brand & will replace the front one at some point also... Is the bike any faster? Can't tell...