Given that it is a 68 that makes it desireable. Add to that they claim it's numbers matching so the vin stamping on the top of the block where the block meets the transmission should match the transmission vin which is stamped where it mates to the block. All that should match the vin stamped on the core support and the trunk. Of course all should match the build sheet. Build sheet should indicate what came with the car so it's possible it was ordered with A/C and the defogger.
There also may be more documents under the carpet however since it was replaced that may not be the case. Looks to have the correct simulated mag caps. They should have a argent or silver backing. 69s were black.
I would say given the market and the examples i've seen lately for sale I'd offer 14K and not go over 17K. Depends on how bad you want the car.