Longlife De Luxe ballpoint pen

Hi - I have my Dads Longlife De Luxe pen with  a commemorative engraving fr=
om 1968. It has sentimental value. My son pulled it apart and I cannot figu=
re out how it goes back toegther correctly. I would greatly appreciate any =
guidance advice on the order of assembly of internal parts and which of the=
 3 outer sections to insert them into

Thanks