Some are very fine threads although without some way of knowing the diameters it's hard to be sure, But some look like brass thread to me, The tap should have tampe dint the shank the dia, the thread type BSF, BSPP, BSPT , Brass, BA etc and a number being the turns per inch. To preserve taps and dies it is worth buying a tin of tapping lubricants say Trefolex, make sit easy to tap and cuts down wear. Frankly I've been buying tools like end millsm slot drills and taps and dies [ where the size is available] from China. Excellent quality and I think on might find that the ones you buy locally made in China anyway and you are just paying a middleman mark up. Recently I needed a long series 5/16" BSF tap. Not something you use a lot but locally would be about AU$ 35, Bought from China on ebay under $3 [ so bought a spare while I was paying postage which was also negligible