je to hovorova(slangova) fraza cize to nemusi byt gramaticky spravne
Podla Oxford dictionary of english:
a chip off the old block (informal) someone who resembles their parent in
character or appearance.
chip – ako podstatne meno znamena ulomok ale
chip off – odseknut, odstiepit
We had to chip ice off the upper deck. Museli sme odsekat lad z hornej
paluby.
Podla nasledujuceho clanku to povodne znelo „chip of the old block“.Potom
to niekto zmenil na OFF a tak sa to teraz pise.
A kedze je to informal phrase tak v hovorovej reci tam rozdiel medzi OFF a OF
nepocut.
Tip: Ak zacnes vo velkom pouzivat tu verziu s OF mozno sa to presadi a opat
vrati k originalu 
The first form of the expression was chip of the same block, meaning that a
person or thing was made of the same stuff as somebody or something else, so
from the same source or parentage. An early example is in a sermon by Dr Robert
Sanderson (at one time Bishop of Lincoln), dated 1637: “Am not I a child of
the same Adam … a chip of the same block, with him?”.
Later that century, another form is recorded a chip of the old block, which
meant that somebody was the spitting image of his father, or continued some
family characteristic. At some point, probably late in the nineteenth century,
this was modified to a chip off the old block, which does nothing to change the
sense, but is the way it’s now usually written or said.