Hi Ray,
I wonder how this bike was described to you? Is it meant to be a "restored original bike"? From what I can see I in the photo, I'd say this is likely a "parts special".
What makes you say it is a TDC? Is the crankcase marked TDC?
To my eye, the cylinder, seat, carby, head stem, magneto, mudguards, tank, rear stand, chain wheel, head light, exhaust system ... all seem to be "unusual" for a 1911 motorcycle. In Australia I've seen may TDC motors, but I've never seen one with a cylinder that looks like this one. To me it looks like it's from a 3 3/4 h.p. Precision of about 1914. (TDC motors were so similar to Precision that many oparts will interchange.)
By the way, I once read a comment from a relative/employee (I forget which) that TDC never made complete motorcycles. In Australia, however, locally assembled bikes were often given the name of their motor - JAP, Precision, and possibly TDC.
Value? Some people don't seem to care whether the bike they ride looks anything like a bike made in the day - if you're one of these people, pay what you wish. If you're looking for a proper veteran, perhaps you could do better elsewhere. If you intend to buy, I suggest you get the seller's description of the bike and its "history" in writing - you may want it later.
Leon