"[2] On 18 October 1748 Hasselaer was among the High and Mighty Lords of the States General of the United Provinces who were signatories to the Treaty of Aix-la-Chapelle (1748) which ended the War of the Austrian Succession.

[3] Hasselaer was a director of the Indian Council when, in December 1748, Joan Gideon Loten obtained a position as a Councillor extraordinary.

At this time the Dutch were trying to catch up with the English in navigational knowledge and skills, and Hasselaer assisted in this process.

In November 1776 Utrecht University acquired an "extra fine octant in its case" made by Jonathan Sisson (c.1690-1747), a London-based maker of scientific instruments, from this collection.

[6] Hasselaer, as regent of Amsterdam, was in contact with Sisson and with his Amsterdam-based brother-in-law Benjamin Ayres, also an instrument maker.