After looking at thousands of stamps over many years you can kind of tell what looks normal and what does not. That is what most people use to form an opinion. Of Course, there are stamp anomalies that only the most experienced people can form an expert opinion on, and I am not one those people. My comment about it looking funny, means just that. It looks like something happened to this stamp after it left the factory to disturb the stamp and pad finish, and possibly at the factory to cause the last 3 digits to be deeper.
Here are some good pads and stamps, and you can see the last 2 digits on one of them look deeper, so that could happen.
Bottom line is, does someone want to but all that time and effort in on this car, and have a funny looking stamp? In my opinion, its way overpriced for what's there, what it will take to get it finished, and what the final product will be worth. For some unfair reason, the 68 model year is worth less than the 69, and is harder to prove than the 67 and 69 due to trim tag information missing.