I looks like a Collins No. 1005 bolo but at the weight you say it is it might be a copy that someone has made??? Sorry to not be of much help.
Best,
Robert
Robert, I think you nailed it. I looked up the Collins No. 1005 and this looks like the Type 2 version. The blade has been polished hard over the years and if there is a Collins mark there I can't see it with my bad eyes.