Between B E R T the rim seems a bit thin, by the 1 9 7 it looks a bit thick. Is this an error, off center strike? I don't see any difference on the reverse, just the obverse.
That is very typical for the 71 half. Also, if you see a coin that is a little bit "off center" on one side but the other is centered fine, that is a misaligned die. Also very common with no premium.