Visje
Thanks for thinking that I might be able to answer this one. I have a few notes on Smulders/Gusto, and I hope that these will be useful to you.
The Utrecht firm of AF Smulders, which I think was also known as Utrechtse Ijzergieterij & Machinefabriek, set up the Gusto shipyard at Schiedam and it was opened in 1905. From the very start it was known as the "Gusto" shipyard. In various editions of Lloyd's Register (LR) I have here, starting with 1912, it seems that the Smulders and Gusto names were "interchangeable", and while all built in the same shipyard, some ships are shown in LR as built by Smulders and others by Gusto. For example, Wassenaar (built 1917) is shown in LR as built by Werf Gusto, but Ellewoutsdijk (1920) is shown as built by Werf Gusto Firma A Smulders. The earliest ships are shown only as built by Smulders.
Importantly, the 1932 LR index of shipbuilders shows the company as
SMULDERS, A.F., N.V. WERF GUSTO v/h FIRMA,
which should more properly be
N.V. WERF GUSTO v/h FIRMA A.F. SMULDERS.
I would guess that the v/h (which as you know is voorheen [fomerly]) first appeared in LR about 1929-30, but I cannot check this out until January when I am next at LR headquarters.
However, the Smulders name seems to be the keyword in the listings in many directories published in the UK up to at least 1954, when Gusto became the preferred name, even though the Smulders family still owned the company.
There are many Dutch language websites that have news items on the Gusto shipyard, and there are also many websites that cover Smulder family subjects. Can I suggest that you do a Google search and have a look through these.
Regards
Roger