1-3/8" American National 16 Series thread.
It's not really common.
Wholesale Tool Company have a tap advertised for $95 cheap ("special threaded hand taps WT",page 6) and 2-1/2" button die (currently in stock,listed under "dies" then "2-1/2" high speed special dies") for $37.
Do a Google-search;they have a website.
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