Messy Worktable in The Studio

Can you find the answer?  The object in question
is sitting right there between the brush holder and
water jug.  My son, his family and their vicious
dog Trixie were here for the New Year's Holiday.
They kept me busy so there was little activity in
this work area.  When I finally got down there, I
found this scummy, nearly-empty coffee cup from
before Christmas.  The coffee had evaporated but
it left a interesting circles in the cups interior.
On the table you see the beginnings of a new watercolor.
Today, it should begin to take shape.
Thanks everyone for participating.  It was fun!