When I started work in Sept 1959 as a GPO apprentice telephone technician, my first job was learning how to run jumpers across the MDF (flexibility point in all exchanges) and this involved using rather large copper soldering irons of which there were two, one of which was being (re)heated in a gas fired heating device, whilst the other was in use. Yes, they had to be filed and tinned before use, and no, these were not axe shaped.
Later, we started using electrically heated irons which worked from the exchange 50V supply (40V in manual exchanges). As you might expect, these were much safer.
Mains operated electric soldering irons were available, but were not to be used in telephone exchanges due to the possibility of mains getting onto the telephone circuits in the event of a failure of the iron's insulation.
Good grief, that's 61 years ago!
Peter G. Shaw