Interesting, as far as boilers not made commercially made, a steel boiler for a model does not need to be joined by a coded welder, however, samples of welds pertinent to boilers have to be produced to the boiler inspector before starting the build, samples to be not more than 12 months old. TIG welding copper boilers is permitted, same as above. This from the 'Blue Book'. But, this only applies to members of clubs that issue certificates on behalf of members of the British Model Engineering Liaision Group.
