Advice please :-)

Looks like nice original Seamaster with original box and papers. The papers will likely identify the reference number number and serial number and assuming they are from your granddads original purchase they add appeal and value, as does the box and probable original buckle.
Take some additional photos of the numbers on papers and the back of case. There may be small hallmarks on the underside of lugs if it’s 14k or 18k gold. All the identifying numbers are on inside of Caseback and movement will have serial number take to watchmaker to open and photograph inside.

May be 14700? Here’s one to compare