Identification of shelf brackets

I have a steel sheet metal cabinet that uses the pictured brackets to hold up shelves. It has a runner in each corner on the inside, with slots which the brackets fit into with a little tooth on the back, which is 3/8" wide (shown below). The shelf sits on top of them. Similar to a push in shelf bracket. I would like to install some more shelves, but do not know what the brackets are called, preventing me from getting some more. Can these be identified to assist in purchasing some?

brackets installed into slots brackets installed into slots

top of brackets top of brackets

back of bracket showing tooth back of bracket showing tooth

bottom of bracket showing tooth bottom of bracket showing tooth