It's a Costo. It is very closely related a Robust, I think they are the same gun with different names on them. Manufrance produced like a million of them, they were work-a-day guns for the masses.
There was some sort of factory running joke on the names, that escapes me at the moment, but, the truth is you can't really buy anything like either of these guns today. Solid hunting implements, usually pretty light and with adequate wall thickness and meat in the chambers.
Watch for pitted barrels. Most won't sell for more than 1K. Good deals.
Best,
Ted
