This URL lists the mass of Copper-63 as 62.9295975(6) and this other URL lists the mass as 62.939598. These values differ by almost exactly 0.01 which seems hard to explain by experimental error. Why is it that these values differ in a significant digit but have the same less-significant digits? Is one of them a typo of the other? What is the correct value? What is the origin of both of these values?
This discrepancy was noted by commentators in this article about a supposed cold-fusion reactor. According to those commentators, this value is relevant to the cold-fusion debate because it makes all the difference as to whether or not the supposed reaction is energetically feasible. The linked article concerns the same cold-fusion claim discussed in this previous physics.SE question.
EDIT: user9325, voix, and user3673 have indicated that the correct answer is 62.929... I have started a bounty on the origin of both the correct and incorrect values.