What could be meant by something "puts the tin in" someone's "pockets"

Solution 1:

Looking through the whole text there is no clarity as to the use of the phrase.

However there are a few ways the Purser can gain (tin=money) from such floggings.

Others have pointed to the most obvious need to buy a replacement shirt. However it might be possible to buy a shirt from ones "mates", or make one as per the narrator did.

A secondary way the Purser will certainly gain is if the one colted (Candy) who we never hear of again? is to die since the belongings will automatically go to the Pursers Auction (which is described in much detail). But if that was the outcome surely a point would be made later.

With such severe welts "Candy" is likely to resort to alcohol for internal and external use, again under the control of the purser. Although the story would suggest he could if he wanted, go to "Pills" the surgeons assistant.