[Ger-Poland-Volhynia] A new member

[Linda Shepherd]

Hello Everyone,
My name is Linda, I live in France and  have ancestors that span
Brandenburg, East Prussia, Poland and Holland!
I  have just joined this group in the hope some of you may be able to help
me locate information about part of my family that came from East Prussia
and Poland.
At the moment I am researching Johann Heinrich Thim (Thiem, Thieme) I have
quite a lot of information about his work with the Dutch East India Company.
Amongst the records I have is reference to his portrait that may be in a
Danzig archive/museum. It was made following his death in 1696 when his
ship, the Koning William sank on the Flemish coast. The portrait was a
copper etching by a Dutch artist named Blooteling. There is an inscription
on this protrait which reads ' Königlich Polnischer Kammeredelmann und
Inhaber eines Regiments von Fussknechten' This portrait also shows a crest
with the nine pointed count's crown. The text I have, written  in 1937 by
Paul Thiem, a descendant,  reads as follows:
....auf dem Porträtstich befindliches Wappen, welches mit einer neunzackigen
Grafenkrone geschmuckt ist und in dem rot-silber geteilten Schild den das
ganze Schild bedeckenden Anker zeigt, welcher auf seine seemännische
Tätigkeit hinweist und die Unterschrift "J'aspire" trägt. The writer goes on
to suppose that this crest may have been given to him by the Polish King
following his service as 'Kommandant der Festung Weichselmünde in 1683 -
although he questions this.

Here are my first questions:

I wonder, does anyone have access to archives that could check this out for
me?
 Does the original of this portrait exist anywhere?
Is there any further information available about the gift of this crest -
how did he have the right to it?
Are there any pictures of it?
Where was Weichselmünde - what was the history surrounding this period?
Paul wondered whether the Warsaw archives may hold further information about
him - he mentions 'Archiwum Glowny, Warszawa'

The other query I have is about Johann's children. He had four. At the time
of writing, Paul Thiem had been unable to establish what happened to them
after Johann's death. He did not know whether they remained in Holland or
whether they relocated to the fatherland.

As far as I can tell they were all born in Amsterdam:
Barber Thim - 2/06/1665
Jacomijna Thim - 17/04/1670
Geertrudijda Thim - 18/10/1671
Jan Nicolai Thim - 8/09/1673

Thank you for any light you may be able to shed on this for me.
Yours sincerely Linda Shepherd