Larry,
My last Uggie boxlock was a Falcon 12, with a hidden third fastener, in probably 95% condition-and it was a whopping $375 on gunbroker. The biggest problem with that gun was the white line pad that was installed. You can do it, that is, buy very decent boxlocks for under the $600 mark, if you look and are patient. By the way, the bits for Spanish guns all come from the same steel cooperative, and the "soft" parts are not limited to POS guns. The skill set of the employees of any given Spanish gunmaking concern is more relevant than the name on the gun.
The mindset that you have displayed that ALL Belgian guns are knock-off cheapies is flat out wrong, Larry. The gun pictured by me is a good quality A & D boxlock, equal to most A & D boxlocks coming out of France. Further, no gun shot longer, or, better, simply because it is Helice locked. The Verney Carron patent would have you believe otherwise, but, it didn't change our destiny or even change the fact that a well made boxlock from anywhere across the pond would last several lifetimes of hard use.
There is a Charlin listed on gunbroker right now that is at $480, but, sliding breech pricing is all over the map, and not really indicative of pricing on boxlocks, helice guns, or, otherwise.
http://www.gunbroker.com/Auction/ViewItem.aspx?Item=284769470

If a guy waited until this auction ended and offered up $600 for this gun, I'll bet he'd get it. Helice gun, too.

Keep an eye on your meds, Larry.

Best,
Ted