If the chest has some fragile treasure in it (such as glass statues) are there rules for determining whether or not the person smashing it accidently breaks them?
I've seen adventures/modules mention such events, "If the adventurers break the chest open then potion bottles inside are destroyed" or such. I don't recall any RAW rule dealing with it. I think each chest and situation is probably different enough that 1 rule won't work.
Nothing hard and fast, as far as I know, but it's the sort of thing scenario designers (and GMs) are likely to implement themselves.
With a claw hammer, chisel and time I think I could take a chest apart without breaking anything inside - unless there was a trap designed to destroy the contents in which case FWHOOM!
If you were swinging an adamantine greataxe with the intention of breaking in as fast as possible then I could see damaging the contents.
I guess taking it case by case works. I'd also agree breaking off the lock is probably the best way to do it (only exception would be if the lock was adamantine and rest of the chest was wood, as at low levels it might not be possible to do enough damage to get past the lock's hardness.)