Roark believes 1938 more likely.
This is based on really flimsy evidence, though, like:
"he didn't compete in Master's shows when he was eligible!"
"The magazines didn't say that he was especially old!"
"his passport said DoB 1930, but it looked more like 193o, so I think he tampered with it!"
There's really no solid proof for a 1938 DoB, and we should probably just take Beckles at his word, especially as he did produce a passport that documented a 1930 DoB.