Although punctuation variances are common, it is interesting to note that Jim Forte's Postal History Website shows that the postmark for that town was known as "Hammersley Fork" (1893-1972) or Hammersley's Fork (1859-1893). I assume the latter is correct for the cover shown, however, note the apostrophe is missing from the CDS. (Although it could be the apostrophe was left off of only the MOB postmark.)
Also, the addressee of the cover O.W. Wolf, Esq., of North Bend, PA, was Oliver Watson Wolf (1844-1932), born in Jersey Mills, Pennsylvania to Henry M. Wolf and Mary Gamble. Oliver Watson married Martha Jane Harris and had one child. He passed away on August 13, 1932 in Nippenose, Pennsylvania.

The above excerpt taken from page 2 of this newsletter:
http://www.div11-mcr-nmra.info/News...JUL-2011.pdf