This might be a weird question but there are some very strange fluctuations on there. Situations where he's listed at 180+ days before or after taking on other fights at 170ish. https://boxrec.com/en/box-pro/011254 In March 1921 he supposedly fought Al Reich at 182 and then fought Paul Koerner at 170 a few days later. In December 1922, he supposedly fought Joe Burke at 170 and then fought Billy Miske at 182.5 a few days later. What gives?
Its possible he weighed in fully clothed for those higher weights. Notice how both times that happened it took place in the winter or early spring.
Another thing I noticed when looking at this was that both fighters weighed unusually high for these weigh ins, not just Gibbons, so if they werent fully clothed then maybe something was wrong with the scales.
Step on a scale in heavy boots, thick winter coat, your wallet and keys in your pocket, etc. Might not get you 10lbs, but I bet it gets you 5-7.
Back then clothes were made of heavier materials as well so it could definitely get you a good ten pounds heavier, especially in the winter. Its not unheard of for scales to be off though and in both the instances quoted above the opponent was also unusually heavy.
They are accurate in some much as they are his reported/recorded weights. As others have alluded to, sometimes he may have weighed fully clothed and booted, and others not.
If Gibbons was weighing in fully clothed and booted, it stands to reason his opponent would have also, which may explain both fighters being heavier than other recorded weights around that time.
Did they have modern weight cutting techniques back then? If so that explains it. Also yeah clothes adds like 2 or 3 pounds. And I'm not informed on that sort of thing but since everything used more material you'd think clothes would weigh a bit more then?