or more specifically Fe-Ni...I went looking at those litle guys as a source for niclel lams for an DIY choke project. They are only half-inch tongue...so I went to magmetals and see that cobalt( high flux density ) and good nickel are available for 1". Now if I can get rid of some stuff, I'll get some new grid chokes wound. Movin' on up to 1kHy perhaps....One more piece for the amp project. You guys OK with getting an extra-special bit of signal Iron made? It'll cost a bit more, but I have a feeling that it will be more than worth it...
regards,
Douglas