This is the tombstone of the infant son of John and Mary (Tester) Heffner, located in row 7 of Zion Lutheran Cemetery, Chattanooga, Mercer County, Ohio. The marker is inscribed:
J.C. & M.C.
Born & Died
Dec. 24, 1887
Unfortunately there is no record of this child’s birth, death, or burial in Zion Chatt’s records, but he was likely the son of John C. and Mary Catherine (Tester) Heffner.
Their initials were J.C. and M.C. and they were the only Heffner couple with those initials who would have had a child born during that period of time.
The initials J.C. and M.C. are also on their son “Frankie B” Franklin Benjamin’s tombstone, which is also located in Zion Chatt’s cemetery. In addition, John Heffner used the middle initial “C” in the 1900 census. 
I wonder if this child was the twin brother of John Henry Heffner, born 29 December 1887, who the church records say was baptized immediately on 30 December 1887.
The problem is that their birth days do not match. John Henry was born 29 December. The tombstone indicates this child was born and died on 24 December. I guess it is possible, but unlikely, that Mary gave birth to twins five days apart.
John Henry Heffner’s birth is recorded in at least two places, the church records and the probate court records. The Mercer County Probate birth record shows his date of birth as 29 December 1887,  but the birth of his supposed twin brother is not in the probate birth or death records.
John Henry’s birth was recorded in Zion Chatt’s records as 29 December and indicates he was baptized the next day, 30 December. However, neither his supposed brother’s birth nor death was recorded in the church records.
The church records describe John Henry’s baptism as a quick, emergency baptism at the home. That would be understandable if Mary gave birth to twins and one was stillborn or died very soon after birth. Perhaps John Henry was small and sickly when he was born.
There could be several explanations. The tombstone could be inscribed incorrectly, inscribed with either the wrong day or the wrong year. However, Mary had a child about every two years and the year 1887 would be about the right time for another birth in the family.
The tombstone could be weathered so badly that it is being read incorrectly. Or, the church record and the probate record could both be incorrect concerning John Henry, but I doubt that.
We will probably never know the true story, whether these two boys were actually twins or not.
 1900 U. S. Census, Washington Township, Mercer, Ohio, ED 90, p.14B, dwelling 294, family 297, John C. Heffner; database with images, FamilySearch.org (www.familysearch.org : accessed 5 Jul 2015); from FHL microfilm 1241304, from NARA microfilm T623, roll 1304.
 “Ohio, County Births, 1841-2003,” database with images, FamilySearch (www.familysearch.org : accessed 4 July 2015), John Henry Heffner, 29 Dec 1887; citing Liberty Township, Mercer, Ohio; from FHL microfilm 2367095.