Recently an unknown perforation appeared in a Dutch seal of 5 cents, used in the fifties and sixties of last century. The date in the stamp is unfortunately not legible. A part of the name of the office where the stamp has been stamped is clear.

After consulting the information on the website of the Dutch Academy for Philately  it appears to be the auxiliary post office Marsdiepstraat/3 in Den Helder as the only possibility.
Searched in the address books of the Municipality of Den Helder became a possible user in an advertisement found: Helderse Auto Centrale (HAC) (see image).

This company is not yet enclosed in the 1961 address book of Den Helder, but in 1968 and 1971 it is. In the address book of 1974 the name disappeared again.

Of course this does not mean that the perforation was used by this company. The perforation could just as well be HAO or DAH. And if it is the letters HAC, it is not yet proven that they are perforated by the Helderse Auto Centrale.

Hence my appeal: who ever came across this perfin or did you know from which company this perforation was used in the late sixties / early seventies? If you have more information, give it to Ton van Schijndel via Thanks in advance!