A picture would be great .. but see if you can remove the gun safely from the stock without damaging it. If you are afraid of damage then don't do it .. but look around carefully so see if there are any other distinguishing marks or writings on the hidden portions of the metal or the wood.... if there is a buttplate see what's underneath ....
You say it appears to be a side by side marked 6mm on one side and 9mm on the other? Which side is the 6mm and which side is the 9mm? 2 triggers or one? And you seem to think it is a rimfire and I guess you believe this because of the firing pin set-up when you break it open?

I tried looking up "Fiocerl" on the internet and in my books BUT NO LUCK....