ok the a-stamp black chassis are around. this may identify your buggy as a very early 6035. even fewer made their way into kits. for the most part they were sold as replacement chassis with the associated us flag header card part number 6301.
these black a-stamp chassis were most likely left over gold pans that the company had laying around. to update them they would drill for the stealth and reanodize them in black.
now there were also a-b stamp chassis. followed by b stamps and c stamps. the a-b chassis were old a stamp chassis that were drilled with the additional holes for the stealth and then they stamped a b over the a that was already there. you chassis most likely was made ether before this restamping started or was just done on a day when quality control was a bit more lax than normal.
so a good way to look at a black a-stamp is recycled
and it is one of those things that could draw a little more from a collector but remember condition will play a bigger factor than what stamp it has.
also it is had to tell from the pic but does it have both sets of holes for the inline battery setup? it should only have one set of holes for the inline battery and those will be slightly off center if you look at them. the centered inline battery holes were not done from the factory until the later b-stamp chassis.