That’s a Diamond Edge stamp. Diamond Edge was a brand name owned by Shapleigh Hardware of St. Louis. They didn’t make knives themselves but had them made on contract by various manufacturers including Schrade, Empire and others. Diamond Edge was their premium brand and was used on knives, axes, etc. viewtopic.php?f=2&t=59225&hilit=Diamond+Edge#p681444
You can do a search here for “ Shapleigh” to learn a lot more.
How about a picture of the entire knife?