Even the person posting seemed confused, but his supposed answer doesn't exactly sound correct.  I would have guessed maybe it was a commercial gun with no import markings pre 68.

From the listing:
Many have inquired why this pistol's bids were going high. I wasn't aware at the time that I listed it but have since learned that the "C00XXX" serial numbers were issued to the Italian Carbinieri (Domestic Italian Police Forces) prior to import to the U.S.. This was a police issue Beretta. We appreciate your bids! Our mistake is your gain. The sale will go on!

https://www.gunbroker.com/Item/911728126

Derp.

My bad, see you've already covered it from the quote