Event organiser Debbie Hall had hoped for 80 postbox toppers and was surprised to be able to cover nearly 90 of Mr Reeder's collection.
She said it was a chance for people to show off their creations.
She said: "There are a lot of postbox toppers on the Isle of Wight and where are they all?
"They must be in cupboards and boxes and attics, and it was my job to locate them."
Some of the designs included Noah's Ark, The Beatles' Abbey Road album cover and a prisoner that was originally mounted outside a jail.
The event was free to enter and raised money for the Alzheimer's Café by taking voluntary donations.
Pauline Rippon knitted the charity's logo of faceless figures in a boat.
It was made especially for the event and mounted upon one of the oval shaped London postboxes, of which there are none on the Island.
Mr Reeder's collection began when he rescued a wooden postbox from the station at Rhyl in Wales when on holiday and restored it.
He has postboxes from Inverness to Truro and there are a few from overseas including the Republic of Ireland, the US and Gibraltar.
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