These are dialectal forms, particularly common in Western (i.e. Cape) varieties of Afrikaans (cf. Ponelis 1993: 230). As Ponelis (ibid.) notes, the plural forms are much more productive than the singular ones. Dit se is also possible in these varieties (dit se wiel is af - [3SG.N.POSS wheel is off] 'Its wheel is off' - own knowledge).