The auctioneers listed below (alphabetically) regularly hold auctions with a lot of good material from the Baltic States:
119 West 57th Street, Suite 316, New York, NY 10019, USA
+1 212 977-7734
+1 212 977-8653
infocherrystoneauctions.com
https://www.cherrystoneauctions.com
Live auctions every 6 to 8 weeks. Colour online catalogue with free text search.
Steinbeisstraße 6+8, D-74321 Bietigheim-Bissingen
+49 (0)7142 789400
+49 (0)7142 789410
infoauktionen-gaertner.de
https://www.auktionen-gaertner.de/philnet/gaertner/gaertnerweb/Index_EN.html
3 to 4 major international auctions per year. Colour online catalogue with free text search. Also trading at fixed prices under https://www.philatelie-gaertner.de/philnet/gaertner/gaertnerweb/IndexPG_EN.html.
Hasengartenstraße 25, D-65189 Wiesbaden
+49 (0)611 34149-0
+49 (0)611 34149-99
infowww.heinrich-koehler.de
https://www.heinrich-koehler.de/en
2 major international auctions per year. Colour online catalogue with free text search.
Lindenweg 1, D-63877 Sailauf
+(49) 911 560399-0
+(49) 911 560399-66
servicephilasearch.com
https://www.philasearch.com/en?locale=en&
Internet platform for dealers and auctioneers offering stamps, postcards and other philatelic items worldwide, with online free text search.