need help with old time abbreviation on a fire brick.

[VTdigger]

I apologize for no pics, but I don't have a working camera at the moment. but today I was river searching and found an old white fire brick that said Fire brick CoS. Bennington VT. I know fire brick was manufactured in Bennington by the Norton pottery starting in the 1830's I also have one marked Fenton's no. 1 fire brick that's was made in the 1850's by The Untied States Pottery I know what those are and where there from. The one I found today that's marked fire brick CoS has me confused, what does CoS. stand for? Might it stand for Company's? meaning this brick could have been made at another mill in Bennington other than the potterys?