Source : Webster's Revised Unabridged Dictionary (1913)

Sealer \Seal"er\, n.
   One who seals; especially, an officer whose duty it is to
   seal writs or instruments, to stamp weights and measures, or
   the like.

Sealer \Sealer\, n.
   A mariner or a vessel engaged in the business of capturing
   seals.

Source : WordNet®

sealer
     n 1: a kind of sealing material that is used to form a hard
          coating on a porous surface (as a coat of paint or
          varnish used to size a surface) [syn: {sealant}]
     2: an official who affixes a seal to a document