Ref the hammer head - one of the main users were small time farmers - and the one piece of kit they all had was a plough (plow) - it was probably the only mechanical thing they owned, maybe an old Ford as well which doubled as tractor when needed, but most ploughing was done with a horse. Ploughs were bolted together, and if a large stone was hit could be put out of adjustment. The farmers then needed to loosen the nut, knock the part back into line, and retighten. Most iron ploughs were supplied with a combined spanner/hammer, which fitted into a slot or rack on the plough, and was easily lost. An 'all purpose' adjustable spanner was often used when the original was lost or mislaid, and an integral hammer was a 'must'....
