Track cog threading or lockring threading? On the website of a wheel manifacturer, I can find the following specs about the cog compatibility of their track wheels:  


  Our track hubs are then compatible with threaded track cogs of Shimano 1.29” x 24 specification.


Is this possible? I am skeptical, because I can't find any cog that has this kind of threading. For reference, 


EAI cogs specs show "standard 1.370"x24tpi English threading"
Shimano cogs specs say "ISO 1.375" x 24 tpi"


I suspect the specs on the track hubs refer to the lockring threading instead, because that's the only measure I can find through a Google search that actually corresponds, see https://www.worldwidecyclery.com/products/shimano-dura-ace-track-cog-lockring-1-29-24-tpi-left-hand-thread

If I am right and that's the case, what's the threading on the track hub I should assume for the actual cog?
You are correct, 1.29 inch is the lock ring thread. The ISO thread for cogs is  1.375 inch, and almost all manufacturers use it. The other choice is Italian thread, which is 35mm * 24 tpi (note the mix of metric and imperial measures). This is 0.2mm larger, so in practice they can be mixed.