Lets see, you can buy a full page add in a gun magazine for thousands of dollars or skimp on a few bucks shipping and ruin your trade name. Seems like a no brainier to me but not the seller. Most of us hate to admit that we made a mistake. First deny, then strongly deny. He sure has gotten his monies worth of advertising out of this transaction.
The crack was there before the gun left the building. He "might" have missed it, in bad light, but I bet ten bucks if you owned that gun and sent it to him, the dealer, would sure as heck seen and pointed out the crack. Particularity on a maker who is well known for having cracks in this very area.
With the price of restocking a side plated gun about what this one sold for the crack needed to be mentioned. It alone was not a deal killer to me but it should have been known by the buyer. Buy a crack stock at your won risk, and many of us have, and gotten years out of them with no problem. Do not expect the buyer to accept a cracked stock gun for the agreed price if he specifically asks if one is present. Would you expect him to take this gun if the barrels or stock had been cut 4" shorter, if he asked if they were original? I think not.