The compensator FS describes is a Pachmayr Power Pac, hardly an obscure choke device, just not as common as the Cutts. A better design, actually, because the choke tube doeesn't protrude from the front of the comp body. A Model 11 had a sliding safety? I've not seen one of those, must be early guns. I would think that a serial number and chamber proof marks on the Browning in question would answer all questions about Sweet or not Sweet and chamber length.