Cape Verde proof?

Hello all,
 I have this coin: https://en.numista.com/catalogue/pieces4376.html  
in what to appears to be a proof coin, but I find no listing for a proof neither here nor in Krause.

Has anyone else seen one of these, or know anything about it?

You have probably a BU (Brilliant Uncirculated) coin.
I have no reference to Proof coins of this period.

It is a very clean example for sure. Maybe they all had a proof finish? The head on the obv is definitely frosted with a mirrored background, and the reverse looks like a polished unc coin - except for the shell shaped design between 20 and the seal. It is frosted as well. I'll post a scan as soon as I can.