alright people, time to clear the air! I am a CHP gunsmith. brief history. in 1990 we went to the original 4006 with adj. sights, all stainless parts, safety, etc.. incredible gun, lasted 18 years with the dept. bought 4 diff. batches. easy to tell by the CONTROL NUMBERS on the right side of slide, barrel, frame, A, B, C, D series. now most serial # started TVD, THB, TVC, TFL,. in 2006 we went to the factory, sat down with the engineers, directors, and helped design the 4006TSW. and almost eleven years later, I must say im glad we did. its been a great gun for us. now the differences in the TSW, spring loaded decocker, MIM parts, equip. rail as part of the frame, heavier extractor spring, novac sights, E control #, and CHP as part of the ser.#. hope this helps