TSW stands for Tactical Smith & Wesson. The TSW series were modified 3rd generation designs and started about 2000 - 2001. The changes (at least in my understanding) are the optional tactical rail, a full length frame rail for the slide to move on, and the slide and frame were matched to each other.
I will answer your second question with another question. Does your 4006TSW have a squared trigger guard? I have not personally seen a 4006 with the squared trigger guard that came on the 45's or 9mm's. Here is a link to the holsters Bianchi makes for the 4006 TSW.
Bianchi Gun Holsters