Guys I picked this up today it seems to be time period correct. it is very Hefty but has an unmarked blade. This thing is dinged up dirty and grungy and it appears that this gravity knife has a release lever possibly from a first pattern gravity knife as it is Blue or blackened steel. Any help as to verification of authenticity would be greatly appreciated. I have four other gravity knives all different makers_helbig,weyersberg,smf etc. but this is my first unmarked example I have been able to put my hands on. to mee it looks as if the lever release spring on the knife has been replaced but looks like very long ago, along with the repplacement lever im thinking it could just be a period repair?