13 November 1920 and 20 November 1920 - De Zuid Willemsvaart

This ad came out 4 years before Mobaco was put on the market.
It states: Pulko Construction Set, very new, fl. 6.00 and fl 12,50. Prices probably refer to sets 1 and 2, Addo and Baldo, or perhaps for Addo and the Bridge set mentioned in the next ad below.

24 November 1922 - Het Volk, dagblad voor de arbeiderspartij

Two years later, an advertisement from De Bijenkorf ("the beehive"), a high end department store in Amsterdam.
The manual in the detail shows "Bouwspel Pulko" (= construction game Pulko in Dutch), and two sets are offered:
- a set for the construction of Villa's, Mansions, etc. - fl. 3.95
- a set for the construction of bridges, large size - fl. 10.75
                                                                                                                                        Detail:

      
Image courtesy of Alex Geelhoed

24 November 1922 - De Tijd, godsdienstig staatkundig dagblad

Same date, and identical to advertisement above:                                                            Detail:

     
Image courtesy Delpher.nl

15 February 1928 - Batiaviaasch nieuwsblad

This newpaper is from Batavia, today's Jakarta. Apparently Pulko was available in Indonesia, at the time a Dutch colony.

"We end our big sale with a small contingent of toys", including Pulko toys for fl. 1.25.
                                                                                                                                                           Detail:

    
Images courtesy of Delpher.nl

15 February 1928 - Het Nieuws van de dag voor Nederlandsch Indië

Same date, identical ad, also in Batavia:                                                                                               Detail:

     
Images courtesy of Delpher.nl