What does "c/o" or "co" mean on the Diablo 3 trade chat?

I've seen several times that people offer goods for sale on the Diablo 3 trade chat and add the letters "co" or "c/o" what do they mean by it?

From the decisions it seems to be some kind of auction because the messages usually go like:

WTS [something] 50k c/o pst with offers

WTS [something] 100k c/o pst with offers

WTS [something] 150k c/o pst with offers

[someting] 200k c/o going once

[someting] 200k c/o going twice

[someting] 200k c/o sold

What do they mean exactly, and what does the abbreviation stand for?

C/O or CO means 'current offer'.

This refers to either the current price at which the seller is offering the desired item, or the highest bid thus far from another party interested in purchasing the desired item.