Gavin, in both Jawa & Bali, until today, material is recycled. In Jawa during the colonial era railway tracks were a favourite source of material, so the Dutch used to have night patrols on some sections of the rail lines to prevent theft.
Not long ago they built a bridge from Surabaya to Madura. One of the construction problems was that as soon as the bolts holding the bridge together were put in place, those bolts were stolen. Bridge bolts are pretty big and a good source of material for hand tools.
For the kerises that I made myself in Solo I used steel from an old bridge and iron from old cart tyres that I bought from a scrap yard in Solo.
Recently a few pandes in Bali and at least one pande in Solo have been using hightech modern steels in the knives that they make. But the problem is that that they do not understand the special heat treating requirements of the material they are using, so they're just throwing money away and the buyers think they are getting something superior when they are not.
Most pandes that I know in Bali & Jawa Tengah use motor vehicle spring steel for knives and tools.
David, the big hammer head is a pretty common anvil for small work, both in Indonesia and in western countries. Just about anything that is big enough for the intended work can serve as an anvil. My first anvil was a section of railway track, I've taught a few people and they used sledge hammer heads, railway track, pieces of machinery as anvils. The trick is to mount the anvil on a good solid stump and sink that stump deep into the ground, somewhere between half a meter and a meter. The difference between a big anvil and a small anvil (like a bit of rail track or a hammer head) is that a big anvil makes the job faster and easier. I learnt on a 150 year old English anvil that weighed 350 pounds, it was really easy to work on. My own anvil is only 75kg (165pounds) and not as fast nor as easy.
This has probably been seen by a few of you, but it might be of interest to those who have not seen it:-
http://www.kerisattosanaji.com/BANDIFORGE.html