Cool to see that the capitalization of Dutch names was as confusing then as it is now.
The correct way to write that would have been with a capital 'V'. The rule for these surname prefixes in The Netherlands is that they are not capitalized unless it's the first letter of the name. So it's "Peter van Emde Boas" but "Mr. Van Emde Boas".
To add to the confusion, that capitalization rule is different for Flemish names. There the first one in the surname is always capitalized: "Willy Van der Steen" and "Mr. Van der Steen".
And nitpick: you likely meant “Willy Vandersteen” (https://en.wikipedia.org/wiki/Willy_Vandersteen), but that would be a bad example as it, I think, would always be capitalized, also if he were Dutch.