I have had a reply to my query about the 'Polkaart CrA' entry on John Hedley Flowerday's first appearance in the Netherlands Bervolkingsregisters.
The lady at the archives tells me that:
Pollkaart is Politiekaart (police card), a card for registration of a foreigner. Unfortunately these cards are not kept anymore.
So at least I now know what its means. Shame the cards no longer exist as that may have told me more, but it is what it is.
I am very grateful to Veronique for her posts.
Boo