Flaming Bomb mark

Hi all.

I see the flaming bomb mark on various pieces of US militaria. I was wondering what the significance of it is. Also, vcan the letter inside be used to date the object?

I was under the impression that the ordnance mark (crossed cannons) was the standard acceptance mark.

Thoughts, observations etc would be appreciated.

"The flaming bomb was the symbol of the Ordnance Corp. Their brass had it as the Infantry had crossed rifles, the Artillery crossed cannons, and Armor a tank. By brass I mean the branch ID brass worn on uniforms."
found this explaination on another site
Carl