This may be what you're looking for. Not sure about "svitabile", but the term seems to cover a number of different mechanisms.

A combination lock is a type of padlock in which a sequence of numbers or symbols is used to open the lock. The sequence may be entered using a single rotating dial which interacts with several discs or cams, by using a set of several rotating discs with inscribed numerals which directly interact with the locking mechanism, or through an electronic or mechanical keypad. Types range from inexpensive three-digit luggage locks to high-security safes. Unlike a regular padlock, combination locks do not use keys.
https://en.wikipedia.org/wiki/Combination_lock

LUCCHETTO A SEGRETO, o A COMBINAZIONE
I lucchetti di questa sorta non hanno chiave; hanno il manico cernierato che s’infila negli anelli, e la tacca del quale viene ad esser chiusa, come nei precedenti, da una stanghetta. Questa non si apre se non quando i dischi girevoli su di un asse, dai quali è composto il corpo del lucchetto, si trovano in una data combinazione, indicata da lettere o segni incisi nel contorno dei dischi.
http://www.bollettinoingegneri.it

or padlock with hidden keyhole mechanism
see
http://www.museiparma.it/site/?page_id=632
a segreto svitabile (hanno forme diverse, ma in comune il tipo particolare di segreto formato da una parte svitabile che nasconde il foro della chiave),

rare possibly unique brass padlock with hidden keyhole uk ...
https://uk.storeslider.com/rare-possibly-unique-brass-padloc...
Jun 24, 2015 - A rare and possibly unique small brass and iron padlock, it has a hidden keyhole mechanism. At a guess dating to 16th or 17th century.

Lexicon of locks and keys - Historical locks
www.historicallocks.com/en/site/h/historicallocks/dictionar...
This section of the Historical Locks website covers over 200 industry and ... Examples of designations of padlocks in the 17th century. ..... Hidden keyhole.

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Note added at 9 hrs (2015-08-19 01:15:02 GMT)
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see the "four open" lock here
http://www.msc.org.mo/locks/en/exhibits.php

and the lock here
http://www.martinka.com/houdini-trick-lock

https://uk.storeslider.com/rare-possibly-unique-brass-padloc...

In Bloomington, Ind., every experience is educational
www.washingtonpost.com › Arts & Living › Travel
Jul 30, 2010 - Few places offer more museums, stages, scenic strolls and great ... trick boxes, a hidden-keyhole French padlock used to fool burglars,