Trading ERC-20 based token The 12th of February 2017 numerai gave 1M NMR to 12K users. 
NMR is based on ERC-20 (ethereum protocol). I was one of the lucky receivers. A few months later, crypto exchanges started trading with NMR and I sold my share. 

In my country, the authorities started taxing cryptos with retrospective effect.

There is one way I can avoid paying tax: If the crypto was worthless or untradeable at the time I received it.

Question: Was it (theoretically) possible for me to trade the NMR at the time I received them (12th of February 2017)?
It was not on the blockchain at that point. 
It was announced in February:
https://medium.com/numerai/numeraire-the-cryptocurrency-powering-the-world-hedge-fund-5674b7dd73fe

Live:
https://medium.com/numerai/an-ai-hedge-fund-goes-live-on-ethereum-a80470c6b681