There's no year which is generally a weak strike, but there are years when dies got overused so that towards the end of their life they produced weak strikes. This happened especially from 1915 - 1919. Also, the Type 2 obverse (1920 - 1926) is much shallower cut to reduce reverse ghosting, and therefore might mistakenly be thought by the inexperienced as weak strikes. Those latter years, the portrait wears much faster, and if you put an EF example alongside a VF Type 1 obverse, you wouldn't see much difference especially in hair detail. But that's due to redesign, not weak strike. From 1926 ME onwards, there isn't any notable weak strike, though as I've said, any well-used die will produce worse results than early strikes. The General Strike was in 1926 I have always taken the position that if the lions nose is missing it's worn not weak.