Sebring Ohio Historical Society
126 North 15th Street
Sebring, Ohio 44672
Crescent China Company
Back stamp included a sliver of a moon.  Also used a Leigh ware by Leigh Potters stamp surrounded
with an outline of Ohio.  Also used umber tone body coloring.
Used pastel borders or two or more colors, silver trim on  edges and artful placement of decorations.
According to Oldetyme,
1920 to 1926 was called the Crescent China Company
built and owned by F A Sebring
1926 Changed to Leigh Potteries with Charles Sebring, son of F A, as manager
Closed in 1931
1940 property purchased by the Alliance Manufacturing Company
the corner of Lake Park Road and Mahoning Avenue
on the Mahoning County edge of Alliance from
1920-26.  He sold this enterprise to his son Charles
Leigh Sebring in 1926 and C.L. operated it
independently as Leigh Potters, Inc. until 1929 and
then until 1931 as part of the ill-fated American The
Crescent China was operated by F.A. Sebring at
definitely be some overlap in 1926 and perhaps even
into 1927 when the Crescent name was used under
C.L's ownership.  Also, I have seen the square shape
with the serrated corners used under both names.  
Thus, while I would say that, while either scenario that
you describe below is possible, it is more likely that
the shape predates the 1928-9 timeframe in which you
credit Turnbull with designing it.  -according to Frank
Photos from Veronica Quartar