David,
The coins you talk about are used behide the mast and in front of the bolt in the mast step.
A five new pence coin or more than one is used to fine tune the heel position in the step so that the pin is loose in a fore and aft postion.
The chocks in the mast gate hold that position at deck level.
The coins have also been used to buy ice cream when a the suns out!!!
C P 😉