The Royal Mint Annual Report gives a mintage of 35,000 for sets of this ½d and the 1d (see page 17, no distinction is given between uncirculated and proof) . This page also gives the mintage for sets of the decimal coins introduced that year and (on page 69) the circulation mintages for the decimal coins are given. It doesn't give any circulation figures for the ½d and 1d, so one could interpret that as meaning that none were issued for circulation.
I own both (they're pretty easy to get hold of) and both are in very nice condition. That said, you can get 1967 U.K. pennies very easily that are essentially uncirculated because they were only issued a few years before decimalization, so the same could be true for these Jamaican coins, issued just months before decimalization. The evidence suggests my coins came out of sets but I'd like to be a little more certain.
Former Numista referee for banknotes from Ireland, Northern Ireland, Scotland, Wales and Saint Helena.