Back sometime last century, Schrade decided to sell their rejects instead of chopping them up for recycling. But like many manufacturers of diferent products, they defaced the trademark on their blades (labels cut from clothing), so they would not be sold as Schrade quality inspected knives. In the case of Schrade, XX marks the ones QC spotted as rejects. At one time they ground the name and number off like the Emperial Mum on my 7.7 Arisaka rifle. Later, they simply sold them to bulk buyers like SMKW. Usually, the buyers advertised them as "seconds". In the end, knives were slapped together sometimes with parts of queationable parentage, just to push them out the door and reduce the inventory of "work in progress", as well as to meet contracts, but personally I think, to make payroll and utilities. I could be wrong, but that's my story and I'm ss-s-sticking to it!
Codger