They may not be standard thread . Back in the day there were may companies in all industries that made their own taps and dies or that had them made to their own thread sizes . Some gunmakers a in the English trade used cycle makers threads , these have now been long abandoned in favour of a "standard" threads . I believe that some American companies used what I have always called sewing machine threads for example that are or are close to your ANC or ANF not common outside the US. Webley used a set of threads specific to them ,some do have equivalents but again many are now obsolete so you can not readily buy taps and dies to suit.
