Ok, Back in 1990 a gentleman whos cars I work on purchased a 1971 stage one convertible. Now that alot of time has passed and we are now in 2020 we never have had any question about authenticity. I recently have helped him put car up for sale. I recently have shown the car a few times to interested buyers. The question I have is with the vin # on the block. I took a razor blade to the front block area to confirm numbers. The casting number on block is correct and everything else on car is correct. But the numbers on front of block do not start with a 4. They also are not the correct size stamp. The size and style of the "type" matches the stamp between the cylinders. I have added a image of the stampings from behind power steering pump bracket. I cannot figure it out. First of all, very strange job stamping, two zeros over lap. Second back in late 80's and early 90's why would you try to fake numbers this bad if thats whats going on and the cars were not selling for the money they do now. Any help/Input from the Buick community would greatly help me validate this car and put this to rest.