The BladeForums.com 2024 Traditional Knife is available! Price is $250 ea (shipped within CONUS).
Order here: https://www.bladeforums.com/help/2024-traditional/
That may not be the temper line but actually the line where the overcoated steel of the bit meets the softer steel of the body in older two-piece (three piece in double bits) axes. Then the steels rusted at different rates. It is not bad. Looks like a nice axe.