Nice looking hammer. I've had bubble(s) in mine as well, but not quite like in your photo. They persisted for some time, didn't 'eject' in a few days as seems to be your experience. Hasn't happened in some time now, but I don't think there's any reason to be concerned. In my case, it seems the head was 'splitting', since once the bubble did go away, the single head appeared to become 2? The mysteries of marine critters.
