I presume it would be too easy to be archie moore who boxed every year from 35 -63. Its a good marker though
Active every year from 1902-1926, Langford just makes the 25-year cut... but we're looking for someone even further back.
Maher fought every year from 1887-1911, so he too just makes the cut... and unless I have overlooked someone, I believe he was the first:good
Dobbs had a long career, from 1888 to 1914... but he missed 1907, where he wasn't active. At least no fights have been recorded for him that year - but even if he had been active in 07, Maher would have been the first to make it 25 years in a row.