This rifle is from the Middleton collection.  It is a Brizilian Comblain Model M____ .  It is a "long" style steel receiver rifle with shrouded hammer, mounting brass nosecap, bands and buttplate and is chambered for the Brazilian 11.4 x 50R cartridge.  Also interestingly, it sports volley sights.
 

Left side of receiver.  This view clearly shows the "long" style receiver (rifle has an integral lower tang AND the plate mounted lower sling swivel at the lower fron of the receiver.  The Brazilian improvement set screw modification is also evident on this rifle.
 

Pictured from quartering behind showing lowered breech-lever trigger assy and open breech ready for loading.  Note also that this rifle is equiped with volly sight.
 

Good view of the shrouded hammer.  There is a hammer there, but is is hidden below the small curved steel shroud at the back of the breech.  This shroud, with the hammer and breech  block, all lowers to clear the way for introduction of the cartridge.  (see above photo).
 

First Built April 1, 1998.