The assigned number is completely randon, so as Shane mentioned, unless it has been already recorded somewhere, it is unknown.
Now, verifying the chassis is a legit VR4 can be done. The VIN attached along with the chassis number stamped in the firewall can be checked and correlated to the correct VIN sequence for a VR4. If you want to, supply me the info you have and I can check on it. I have a list of all VR4 chassis imported to the US.