It is out of print but may be purchased as The Minutes of the Orphanmasters of New Amsterdam, 1655 to 1663 by Berthold Fernow (V.1 ) (1902-1907) from Amazon.com
Quoting from the preface to this book
"Before New Amsterdam received its charter as a city the Director General and Council of the Province were ex-officio bound " to take cognizance of matters pertaining to minor children, widows, orphans, etc.," and under their supervision the Deacons of the Reformed Church acted as Orphan Masters, but with the incorporation of the village as a city the duties of Director and Council devolved upon the newly created municipal rulers—the Burgomasters and Schepens,—who, at their second meeting on February io, 1653, resolved "that it is necessary to appoint Orphanmasters," for which position they submitted to the Director and Council four names to select two."Under Dutch law, when a person died, and if his or her spouse intended to remarry, the rights of all underage children had to be assured. The Weeskamer (OrphanMasters) were responsible for assuring that children had guardians appointed who would guarantee their rights.
It is easy to be confused by the word ORPHAN in the title, but the orphanmasters dealt with children who had one parent as well as those who had none.
In New Amsterdam, under Dutch law, widowed fathers also had guardians appointed for their minor children. Under the law no one who might benefit from the death of an heir, could be that heir's guardian. Also in New Amsterdam, guardians were appointed no matter whether the surviving spouse intended to remarry or not.
In all the cases I've read through, both in the Amsterdam Weeskamer records and the New Netherland Orphan Masters records, the guardian was a relative of the deceased -- or an impartial and unrelated individual.
If you are looking for an ancestor who may have had reason to be involved with the orphanmasters before 1650 you may be out of luck. According to Howard Swain, who consulted "The Orphan Chamber of New Amsterdam," by Adriana E. van Zwietenin The William and Mary Quarterly, 3rd series vol LIII, no. 2, pp 320- 340, Zwieten says on p. 321
"The records of new Netherland before 1650 contain few cases concerning the 'unfortunate.' The population was small, and the care of orphans and their estates fell to surviving parents and relatives. If both parents died and there were no relatives, the deacons of the Reformed Church filled the void."Anyone seeking records of orphans may also want to consult the online list of names of Almshouse children (orphans) sent to New Netherland (New York) from Amsterdam Holland on the ship De Waegh (The Weigh-House), August 1655
For orphanage records for other locations see Orphan & Orphanage Records which also include Almshouse records for New York City.