Extra ammo and supplies

According to *The Ultimate Guide to Vintage Star Wars Action figures 1977-1985, Han is:

Wearing his Corellian spacer black vest - an article of clothing donned by Corellian mariners which is outfitted with extra pockets to hold extra ammunition and supplies...

https://books.google.co.uk/books?id=2VaYCAAAQBAJ&pg=PA27&lpg=PA27&dq=Corellian+spacer+black+vest&source=bl&ots=8EjEZFLRzT&sig=WoFLfYGSoWnk7svMiG9CaOK4hnw&hl=en&sa=X&ved=0ahUKEwj7sNCmsNbRAhWQHsAKHd8vB1UQ6AEITDAO#v=onepage&q=Corellian%20spacer%20black%20vest&f=false

Extra ammo and supplies

According to The Ultimate Guide to Vintage Star Wars Action figures 1977-1985, Han is:

Wearing his Corellian spacer black vest - an article of clothing donned by Corellian mariners which is outfitted with extra pockets to hold extra ammunition and supplies...